Sterndrives FAQs


Does my Mercury Racing sterndrive product have a California Emissions Warranty?

California does not require engines that produce over 500 horsepower to be covered by an emissions warranty.

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How can I get more speed and horsepower out of my engine?

Boat speed and performance depend on many things like boat hull type and condition, propeller type and condition, and the condition of the engine. You should check these basic items before thinking about modifications to get more horsepower or speed. Mercury Racing engines are built to give the best performance and reliability. Engine modifications can have serious effects on the life of the engine package and may put your warranty coverage at risk. We cannot help you modify your engine.

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Can I install a supercharger/turbocharger/nitrous oxide on my engine?

Mercury Racing has not tested and cannot approve the use of aftermarket products like these. Improper installation and/or application of these type products can cause severe engine damage. Engine modifications can have serious effects on the life of the engine package and may put your warranty coverage at risk. Damage caused by product modifications is not covered by the limited factory warranty. We invest a tremendous amount of time and money in developing Mercury Racing Engines. We are not able to offer technical assistance for modifications to our engines.

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Can I install aftermarket accessories like stabilizer “fins”?

While these add-on devices may reduce the time it takes to get the boat on plane, they may also cause or contribute to abnormal or even unsafe handling of the boat and failure of the anti-ventilation plate. Because it is not possible to know how a particular boat will respond to the use of an aftermarket stabilizer fin without thorough testing, Mercury Racing cannot recommend that such products be used or not be used. Failures caused or contributed to by modifications are not covered by the limited warranty.

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Will modification of my engine or sterndrive void the warranty?

The warranty does not apply to damage or failures caused by use of an accessory or part not manufactured or sold by us. See the appropriate Mercury Racing warranty policy for your product or in your owner’s manual.

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I would like to add SmartCraft instrumentation to my boat. Is my Mercury Racing engine compatible? Can I install this myself?

All current Mercury Racing models are compatible with SmartCraft instrumentation systems. Mercury Marine recommends installation of SmartCraft systems be performed by your Mercury Marine dealer.

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What are the features of SmartCraft?

Depending on the gauge system you choose (System Monitor, System Tachometer & Speedometer, System View, or System View-Race Edition), you can access:

      • Basic Engine Parameters (Oil Pressure, Coolant Temperature, Voltage, Total Run Time, Sea Water Pressure)
      • Boat speed via GPS, paddlewheel, and/or pressure sensor*
      • Sterndrive Trim angle
      • Port, Starboard, and Center Trim Tab Position
      • Steering angle*
      • Transmission/Stern Drive in-gear indicator
      • Inches Traveled Per Engine
      • Fuel, water, and waste levels*
      • Water depth*
      • Water temperature with graph
      • Air temperature
      • Dual engine synchronization display
      • GPS interface – Course Over Ground (COG), Speed Over Ground (SOG), Distance to Waypoint (DTW), Bearing to Waypoint (BTW), Time to Waypoint (TTW), Fuel to Waypoint (FTW), Peak Speed*
      • Engine maintenance records and reminders
      • Comprehensive system diagnostic display
      • Time of day
      • Fuel management, range consumption, gallons remaining, average and instant fuel mileage

*These parameters require additional sensors not included with the engine package or gauge system. Ask your Mercury Racing


      for our full color brochure or call our publications department @ 920-929-5110 and request brochure 90-88354702. It can also be ordered through

Catalog Request


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What type of fuel can I use?

Model Gasoline (Notes 1&2) Additives
450, All 500 models, 525 EFI, and 600 SCi US/CAN – 87 (R+M)/2 98 RON minimum octane major brand of unleaded regular or premium without alcohol

NON US/CAN – 92 RON minimum octane major brand of unleaded regular or premium without alcohol (Note 4)None Required

377 SC, 525SC, 575 SCi, 600SC, 800 SC, 850 SCi, 900 SC, and 1075 SCiUS/CAN – 91 (R+M)/2 minimum octane unleaded regular or premium without alcohol, DO NOT USE Leaded Gasoline NON US/CAN – 98 RON minimum octane major brand of unleaded regular or premium without alcohol (Note 3)None Required




  1. If gasoline with alcohol must be used, periodically inspect complete fuel system for leaks and do not store fuel in boat’s fuel tank for long periods of time.
  2. To increase valve life on all MerCruiser engines, the following recommendations should be considered:
    • Use a propeller that allows engine to operate at or near the top of its maximum RPM range when at full throttle with a normal boat load.
    • Operation at 3/4 throttle setting or lower is recommended. Refrain from prolonged operation at maximum (full throttle) RPM.
  3. If unleaded gasoline is not available, use a major brand of leaded gasoline.

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Can I use reformulated or oxygenated fuels?

Reformulated (oxygenated) gasolines are required in certain areas of the USA. The two types of “oxygenates” used in these fuels are alcohol (ethanol) or ether (MTBE or ETBE). These reformulated gasolines are acceptable for use in your MerCruiser engine. If the gasoline in your area contains either methanol (methyl alcohol) or ethanol, you should be aware of certain adverse effects that can occur. See your operation and maintenance manual for details.

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Can I use octane fuel additives?

Mercury Racing does not recommend octane buster for any Mercury Racing Products because we have not validated compatibility with the engines, nor do we know the octane rating of the fuel after it is mixed.

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What type of oil should I use? Can I use synthetic oil?

To help obtain optimum engine performance and to provide maximum protection, we recommend the use of Mercury Precision 4-Cycle 25W-40 Marine Engine Oil. This oil is a special blend of 25-weight and 40-weight oils for marine engines. If not available, a good grade, straight weight, detergent automotive oil of correct viscosity, with an API service rating of SH,CF/CF-2 may be used.

In those areas where Mercury Precision 4-Cycle 25W-40 Marine Engine Oil or a recommended straight weight oil is not available, a multi-viscosity 20W-40 or, as a second but less preferable choice, 20W-50, with API service ratings of SH,CF/CF-2 may be used.

IMPORTANT: The use of non-detergent oils, multi-viscosity oils (other than Quicksilver 25W-40 or a good quality 20W-40 or 20W-50), synthetic oils, low quality oils or oils that contain solid additives are specifically NOT recommended.

The table below is a guide to crankcase oil selection. The oil filter should always be changed with the engine oil.

Air Temperature Oil Type
All Temperatures Mercury Precision 4-Cycle 25W-40 Marine Engine Oil
Below 32? F (0? C) SAE 20W
32-50? F (0-10? C) SAE 30W
Above 50? F (10? C) SAE 40W


This crankcase oil recommendation supersedes all previously printed crankcase oil recommendations for Mercury Racing gasoline engines. The reason for this change is to include the newer engine oils that are now available in the recommendation.

Older owner manuals, service manuals and other publications that are not regularly updated will not be revised to show this latest engine oil recommendation. Current owners manuals, service manuals and other service publications that receive regular updates will receive this revised recommendation the next time they are updated.

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What are the specifications for my Mercury Racing engine?

A general listing of specifications is included in our Mercury Racing product section. Your owner’s manual also includes some specifications. Additional technical information can be found in the appropriate service manual for your engine model, or you can check with your local authorized Mercury Racing dealer.

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Where can I get factory service manuals, parts manuals, or owner’s manuals?

You can call Mercury Marine publications at (920) 929-5110 or order online thru the Parts Express or through the Dockstore on this website. Please have your engine, or sterndrive serial number or part number of the manual available.

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I need to replace my existing engine. What will fit?

Due to the large number of different engine/boat configurations and the changes made to engine packages over the years, we suggest you contact your dealer, engine power center and/or boat manufacturer for specific guidance in your case.

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How do I obtain horsepower curves, torque curves, or fuel consumption data?

Horsepower and torque curves are not published because they are considered confidential company information. Fuel consumption data is not published because it is affected by factors beyond our control, such as boat hull type, temperature, humidity, altitude, gear ratios, propeller, etc. In some cases, fuel consumption or other performance data is available from your boat manufacturer for a specific boat/engine combination.

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I want to upgrade to a new-style sterndrive with my existing engine and transom. Is this possible?

There are many factors which determine the proper sterndrive for a given engine. A different sterndrive may physically bolt to your existing transom assembly, but it may not be a good match for your engine and boat. An Alpha Generation II sterndrive will not fit where an R/MR/Alpha I drive was used. Alpha and Bravo series sterndrives cannot be interchanged. In some cases it is possible to interchange members of the Bravo drive family. We recommend contacting your dealer or engine power center for specific guidance before undertaking any type of sterndrive replacement, upgrade, or repower.

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I want to upgrade to a newer engine and use my existing sterndrive and transom, what will work?

There are many factors involved in replacing your marine engine; newer current engines will not directly backfit to older style sterndrives and transoms. We recommend contacting your dealer or engine power center for specific guidance before undertaking any type of engine replacement, upgrade or repower.

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I want to upgrade to a more powerful engine. How much more performance can I expect?

This depends on many factors such as hull type, weight distribution, maximum horsepower rating of the boat, etc., and cannot be accurately determined without more information. We suggest you contact your dealer, engine power center, or boat manufacturer for specific guidance in your case.

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On a hot day after I run the engine for a while then shut down, the engine won’t restart or it starts and idles fine, but when the throttle is advanced the engine bogs down or quits running and will not restart. Why?

It sounds like your engine may be vapor locking. One factor that contributes to vapor lock is fuel. Fuels produced for use during the winter and early spring months around the United States are designed to vaporize at a lower temperature. This lower vaporization point can cause the fuel in the boat supply lines and engine fuel system to vaporize prior to being used. Another contributing factor to vapor lock is a restriction in airflow into the engine compartment. Make sure that lifejackets, fluid containers or other equipment have not restricted the airflow.
Other items that will help to reduce vapor lock are:

  • Letting the engine idle for 3-5 minutes before shutting it off.
  • Opening the engine cover to let the hot air escape.
    Always reinstall the engine cover before starting the engine.
  • Operating the bilge blower to remove the hot air.

If these items are OK, an authorized Mercury Racing dealer can perform additional tests on the fuel and ventilation systems.

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Can I use an automotive longblock or shortblock to replace my Mercury Racing engine?

No, an automotive block cannot be used for several important reasons. The Mercury Racing ECMs (electronic control modules) are specifically calibrated to each of our engine models. It would not be possible to determine the effect on the performance or compatibility with an automotive engine. In addition, automotive engines are not equipped to endure the high rpm duty cycles and harsh environment that marine engines see. Further, some of our engine components are unique to marine engines, such as the welch plugs, camshafts, cylinder heads, head gaskets and pistons.

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My engine diesels, or runs on, after it is shut off. What causes this and can it be eliminated?

Under certain conditions, carbureted engines may “run on” after the ignition key is turned off. This condition is rarely caused by a defect in the engine itself. Usually, a combination of external factors is responsible. These factors include, but are not limited to, the type and formulation of fuel used, the boat’s engine compartment ventilation system, ambient air temperatures, excessive engine compartment temperatures, how quickly an engine is shut off after running at cruise or higher rpms, elevated engine idle rpm setting, use of spark plugs with an incorrect heat range, deposits on the spark plugs or in the combustion chamber, etc.

There are some things you can do to minimize a “run on” condition. Most importantly, allow the engine to idle for a few minutes before shutting it off. This helps the engine to normalize at idle rpm. Other suggestions include having your dealer verify the engine idle mixture, idle rpm and timing are correct. Try a different brand of regular fuel or try premium fuel. Use spark plugs that are in the next colder heat range. Most of these are changes that should be made by your local authorized Mercury Racing dealer. Our company has provided information to authorized dealers to help them assess your situation and to correct or adjust the contributing factors.

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Is there a factory authorized repainting procedure for my sterndrive?

Yes, Mercury Racing has a refinishing procedure available. For best results we recommend this procedure be performed professionally.

Refinishing procedure:

This procedure should be used in refinishing MerCruiser sterndrives and transom plates. This procedure will provide the most durable paint system available in the field. The listed materials should be purchased from a local DITZLER AUTOMOTIVE finish supply outlet. The minimum packaged quantity of each material shown is sufficient to refinish several sterndrives and transom assemblies.

1 QT. DX-533 Alumiprep #33 metal preparation
1 QT. DX-503 Alodine #1201 conversion coating
1 QT. DP-40 Non sanding Epoxy Primer zinc chromate primer
1 QT. DP-401 Catalyst for DP-40
1 QT. DAR-9000 Acrylic Enamel-black topcoat
1 Pt. DXR-80 Delthane Ultra-additive for acrylic enamel
1 QT. DTR-602 Acrylic Enamel Reducer-temperature range 70-90 degree F.


  1. Scuff sand to remove all blistered paint and roughen factory finish. Remove sanding dust.
  2. Follow manufacturer’s recommendations and instructions on the individual containers.
  3. Apply DX-533 (Alumiprep #33) to clean and condition the aluminum.
  4. Apply DX-503 (Alodine #1201) brush on chemical conversion coating for aluminum.
  5. The DP-40 (Epoxy Chromate Primer) mixed with DP-401 Catalyst can now be applied. A .75 mil film build is recommended.
    NOTE: Allow 30 minute induction period for permeation of the epoxy chromate primer and the catalyst prior to application.
  6. The topcoat consists of DAR-9000 Acrylic Enamel Black and the DXR-80 Delthane Ultra additive, and DTR-602 Reducer. It is a polyurethane acrylic enamel system which provides fast drying, durability, high resistance to corrosion and good color and gloss retention.
  7. The type of spray gun used will determine the proper reduction ratio IMPORTANT: DO NOT use any type of aerosol spray paints, as the paint will not properly adhere to the surface, nor will the coating be sufficiently thick to resist future paint blistering. NOTE: DO NOT PAINT SACRIFICIAL ANODES.

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The paint on the top of my sterndrive is dull and seems to have some type of deposit adhering to it. How can I make it look nice again?

The dullness comes from mineral deposits in the water. When the boat is on plane, the top portion of the sterndrive is out of the water. As the water evaporates from the top of the sterndrive, it leaves behind mineral deposits. You can remove them by using a liquid cleaner for bathroom tub and tile, followed by a coat of wax to help protect the surface.

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What’s the best propeller for my Mercury Racing engine?

Your engine should be propped so that it operates at or near the top end of its recommended rpm range at wide open throttle with a normal boatload (fuel, gear, people, etc.) An engine that does not reach the rated RPM at wide-open-throttle is in an “overpropped” condition, resulting in “lugging the engine.” This high-torque operation puts a tremendous load on the pistons, crankshaft, and bearings in your marine engine.

On the other hand, an engine that revs past the recommended RPM will have higher than normal wear and can also be damaged.

Propping is not an exact science and may require some trial and error. The maximum RPM your engine can achieve is dictated by propeller pitch. Generally speaking, one inch of propeller pitch equals 150-200RPM. To increase your engine RPM, you should decrease propeller pitch and vice versa. Your local authorized dealer can assist you in choosing the best propeller.

Initially, the prop on your boat is selected by the boat manufacturer and/or selling dealer. However, the way you load your boat (people, fuel, gear, etc.) may indicate that a different prop is best for your use. Please notify your dealer immediately if your engine cannot reach the proper rpms at wide-open throttle.

We also publish a very informative booklet on propping “Everything you need to know about propellers” (#90-8614492). You can order through our Publications office 920-929-5110.

You may call the Mercury Racing Prop Shop at (920)-924-2037 for additional information.

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What are the differences between aluminum and stainless steel propellers?

Aluminum is by far the most popular material used today for recreational boat propellers. It is relatively low in cost, has good strength, good corrosion resistance, and is easily repaired. However, compared to stainless steel propellers, aluminum propellers are more easily nicked or bent. Stainless steel is the strongest, most durable of all materials used for propellers. In fact it is about five times stronger than aluminum. This is its greatest advantage. The strength of stainless steel propellers will help maintain engine performance because these propellers are more resistant to the small nicks and bends normally found on aluminum propellers, often after running for a short period of time. Blades cast of stainless steel can be made thinner for better efficiency. Stainless steel is much more resistant to corrosion. Stainless props can be repaired easily, although more expensively than aluminum. They can cause some corrosion on nearby aluminum surfaces in saltwater if good anodic protection is not used. An aluminum propeller can usually be replaced with the nearest size and blade equivalent stainless steel propeller.

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What is the difference between 3-blade and 4-blade propellers?

Four blade propellers:

  • Plane the boat faster than 3-blade propellers
  • Keep the boat on plane at a lower speed
  • Give improved mid-range speed at the same rpm as a 3-blade propeller
  • Provide quicker acceleration than most three-blade propellers
  • Run smoother than 3-blade propellers
  • Have better holding power in rough conditions
  • Are less likely to ventilate in sharp turns
  • Provide better low-speed handling
  • Are usually not quite as fast on the top end as a comparable three blade propeller

You may visit the propeller section of this site for additional information.

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How can I improve hole-shot and top speed performance?

No single propeller can deliver both optimum hole-shot and top speed performance. You will need to decide which aspect of performance is more important to you and select a propeller that is best suited for that purpose. You may visit the propeller section of this site for additional information.

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My stainless steel propeller is turning white, or is rusting or discolored. What can I do about this?

Stainless steel propellers can discolor and form areas of light rust. Brushed finish stainless props are more susceptible than brightly finished stainless steel props. Rust stains can occur from polluted water, galvanic corrosion from the boat or marina, or from oxygen depletion. The propeller can be easily cleaned with rubbing compound or Scotchbrite. Do not use steel wool. After cleaning, use chrome polish to protect the finish. Stainless steel props can also turn white from calcium or lime in the water. In this case, clean the prop with household mineral bath and tile cleaner. Again, do not use steel wool. Follow up with chrome polish to protect the finish.

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How do I winterize my Mercury Racing product?

Because of variations in models, it is not possible to include this information for all of our products on this website. We recommend that you have this procedure completed by an authorized dealer. The raw water section of the cooling system must be COMPLETELY drained for winter storage, or immediately after cold weather use, if the possibility of freezing temperatures exists. You can refer to your owner’s manual or service manual for the location of the drain plugs. Failure to do this may result in trapped water causing freeze and/or corrosion damage to the engine. Damage caused by freezing or improper winterization IS NOT covered by the Mercury Racing limited warranty.

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Do I need to put antifreeze back into the cooling system after draining?

It is not essential to fill the cooling system with antifreeze if you are absolutely sure that no water remains in the system. However, for added assurance we recommend that this be done. Damage caused by freezing or improper winterization is not covered by the limited factory warranty.

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Can I use propylene glycol (RV antifreeze) in my engine?

Propylene glycol antifreeze with a rust inhibitor is approved for use in the raw water cooling system for cold weather storage purposes ONLY. However, if your engine is equipped with a closed cooling system, you should always use a 50/50 mixture of ethylene glycol antifreeze and water in this system. Even if you don’t live in a freezing climate, you should still use an antifreeze/water mixture rather than plain water. Antifreeze mixtures have superior anti-corrosion and boil over protection properties.

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How many drain plugs are on my engine and where are they located?

For specific information you should consult your owner’s manual, service manual, or check with your local authorized dealer.

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Should my sterndrive be stored in the up or the down position?

If you store your sterndrive installed on your boat, you should keep it in the down position. Otherwise, the rubber bellows in the transom assembly can become permanently deformed and fail.

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Do I still need to have winterization performed by my dealer if I have a self-drain system on my engine?

The drain system on your engine is NOT intended to replace full winterization. It is for extending your boating season by allowing the cooling system to be drained after use if there is a risk of light freezing weather and you will be boating the next day. For full extended winter storage, after completely draining the cooling system, Mercury Mercury Racing recommends the use of propylene glycol antifreeze (with a rust inhibitor for marine engines) in the seawater section of the cooling system. The fuel system must have fuel stabilizer added and the system must be fogged with 2-cycle oil. We strongly recommend that your product is winterized by an authorized Mercury Racing dealer. Damage caused by freezing or improper winterization is NOT covered by the limited factory warranty.

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Where can I find the part numbers for specific engine or sterndrive components?

This information is published in our parts manuals or available from authorized dealers. You may purchase a parts manual by contacting Mercury Marine publications at (920) 929-5110 or order on-line from our Parts Express section of this website. In either case, you’ll need your engine serial number, and possibly the sterndrive or transom serial numbers, or the manual part number to order the proper manual.

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What is the warranty on parts?

Parts and Accessories installed on Mercury Racing products that had product warranty duration of less than one (1) year, carry Limited Warranty coverage for a period of time equal to that, and not greater than the duration of the limited warranty originally provided with the parent product. The repair or replacement of parts, or the performance of service under this warranty, does not extend the life of this warranty beyond its original expiration date. Unexpired warranty coverage can be transferred to a subsequent purchaser upon proper re-registration of the product. For specific details, contact your local dealer.

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The dealer says my part is no longer available. What am I supposed to do? Do you have something that will work in place of it?

Mercury Marine makes every effort to provide service replacement parts as long as possible. Many times, older part numbers will supersede to a newer part number or a replacement kit. In some cases, service parts for older models are not available. Mercury does maintain a list of dealers nationwide, who carry non-current parts inventory. If you have the part number for a particular part you need, contact the Mercury Obsolete Parts Locator Service at 1-800-558-6300.

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Can you cross reference parts to Fram, GM, NGK, etc?

With the exception of spark plugs, we do not cross-reference parts. Approved alternate brand spark plugs are listed in the service manuals or owner’s manuals and include AC, Champion, and NGK.

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What is the difference between auto/marine parts? Can I use auto parts on my engine?

Electrical, ignition, and fuel system components on Mercury Racing engines are designed and manufactured to comply with U.S. Coast Guard rules and regulations to minimize risks of fire or explosion. Use of replacement electrical, ignition, or fuel system components, which do not comply to these rules and regulations, could result in a fire or explosion hazard and should be avoided. Also, many other components on Mercury Racing engines are designed and manufactured differently from standard automotive parts. Marine engines operate at or near full-throttle for most of their lives. They are also expected to operate in both fresh and saltwater environments. These conditions require numerous special parts. Care should be exercised when replacing marine engine parts as specifications are quite different from those of the standard automotive engine.

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Where can I buy genuine Mercury Precision Parts and how much do they cost?

Mercury Precision Parts are sold only through authorized dealerships. Your local dealer can provide you with the retail price of these parts. Retail prices may vary in your area. Also, you can visit Parts Express on our website.

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Is there a closed-cooling (fresh-water) kit available for my engine?

We offer closed-cooling kits for most Mercury Racing engines. However, there are some newer products for which a kit is not yet available. Please check with your authorized Mercury Racing dealer to determine if a kit can be ordered and, if so, what other components may be required along with the kit.

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Are there closed-cooling (fresh-water) kits available to backfit older engines such as the 500EFI/CARB, 525SC, etc…?

No, there are no kits available to backfit these older engine models.

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Is it better to change my engine oil/gear lube at the beginning or end of the season?

It is better to change the oil and gear lube at the end of the season, prior to storage. Lubricants naturally accumulate moisture, combustion by-products, and other contaminants during use. It can be detrimental to store an engine or drive with large amounts of these contaminants present.

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How often should maintenance be performed?

Maintenance intervals vary depending on the specific engine and drive model. Recommended maintenance intervals are included in your owner’s manual or service manual.

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How often should I change my sacrificial anodes?

Because they are self-sacrificing, the anodes must be inspected often and replaced when 50% consumed.

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Should I use Premium Blend or High Performance gear lube in my sterndrive?

High Performance gear lube is required in all Bravo and Alpha I Generation II sterndrives. It is recommended for use in all older sterndrives as well. Premium Blend and High Performance gear lube should never be mixed. Be sure to drain the unit completely if switching from one type of lube to the other.

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Can I use Split-Fire spark plugs?

Mercury has not tested and cannot approve the use of split fire spark plugs. Incorrect spark plugs can foul, cause radio frequency interference, cause the engine to run poorly, and may cause severe engine damage from detonation. Your warranty does not cover damage caused by the use of products not recommended by Mercury Racing. The operation and maintenance manuals list the recommended spark plug for your engine. Authorized dealers have cross-reference charts for tested and approved alternatives.

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My owner’s manual lists the oil capacity for my engine, but when I change the oil it won’t take that much without being overfilled. Why?

The engine oil capacities given in the owner’s and service manuals are approximate and indicate what the capacity of the entire lubrication system is. A small amount of oil remains in the crankcase, oil lines, etc. This is why it is difficult to get the indicated amount of oil in the engine without it being overfilled. You should always fill the crankcase according to the dipstick when the engine is level, preferably with the boat at rest in the water. If the oil is at the full mark on the dipstick, then it is at the proper level regardless of how much you put in. It is important not to overfill or under fill the crankcase. The engine oil level should always be between the add and the full marks on the dipstick.

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How often should I flush my engine in saltwater use?

For maximum corrosion protection, we recommend that the engine be flushed with freshwater after each saltwater use.

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Do you have a freshwater flush kit to flush the engine while in the water?

No, we do not offer a kit that can be used with the engine in the water. Currently we offer a flush kit for all sterndrive (except Bravo One Performance and Blackhawk) and inboard (V6 & small-block V8 only) engine applications. This flush kit is intended for use out of the water only. See your Mercury Racing dealer for details on the kit and additional components that will best suit your needs.

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Why do I have to periodically check my engine alignment and lubricate the engine coupler?

With time and usage, the engine will sometimes get out of alignment with the transom assembly and sterndrive. For longest engine coupler life, it is important that the engine alignment be as accurate as possible. We recommend using Quicksilver Engine Coupler Spline Grease for proper lubrication. Damage caused by improper engine alignment or lack of lubrication is not covered under the limited warranty.

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Do you have any tips for do-it-yourself maintenance?

If you are a person who likes to do-it-yourself, here are some suggestions for you:

  • Present-day marine equipment, such as your Mercury Racing power package, is an advanced technological piece of machinery. Electronic ignition and special fuel delivery systems provide greater fuel economies, but are also more complex for the untrained technician.
  • Do not attempt any maintenance or repairs which are not covered in the service manual unless you are aware of the precautions and procedures required. Your safety is very important to us.
  • The service manual is written for the trained technician. Do not attempt repairs if you do not understand the procedures.
  • There are special tools and equipment that are required to perform some repairs. Do not attempt these repairs unless you have these special tools and/or equipment.
  • Please do not contact the dealer, service office, or the factory to request troubleshooting help or to request the repair procedure. It is difficult to diagnose a problem over the telephone.
  • Remember, your authorized dealer is there to provide service for your power package. Dealers have qualified, factory-trained technicians.

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What kind of spare parts should I carry on my boat for my Mercury Racing?

Some suggested items would include a floating prop wrench, a spare prop and attaching hardware, spark plugs, belt(s), oil, power trim and steering fluid, High Performance gear lube, water separating fuel filter.

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For stern drive owners – What do I need to know about corrosion?

The good news is that corrosion can be prevented! Marine corrosion is a fact of boating life, but you can protect your investment with diligence & proper maintenance. As the boat owner, YOU are the most important key to effective corrosion protection. Here are some things you should know:

  1. All Mercury Racing sterndrives come standard with aluminum sacrificial anodes & 3-year warranty against certain types of corrosion (see your owner’s manual for more details)
  2. Bravo sterndrives are also equipped with a MerCathode, optional on Alphas.
  3. Magnesium anodes are suggested for fresh water use ONLY & can be purchased from your authorized dealer.
  4. Anodes & sterndrives should be inspected on a regular basis for signs of corrosion. Do not paint anodes.
  5. Not all anodes are created equal. Don’t sacrifice your sterndrives protection with the use of poor quality after-market anodes.
  6. The MerCathode should be tested annually by an authorized dealer for proper operation. Do not paint or power-wash the MerCathode.
  7. Your particular boating environment may require that you install additional anodes or other protective devices.
  8. Whenever you add stainless steel accessories (for example like props or trim tabs) it’s a good idea to have the corrosion resistance checked to make sure it is still adequate
  9. If you use shore power, you should have an approved galvanic isolator installed to protect against stray current corrosion (electrolysis) from your dock, from your boat’s accessories or from other nearby boats.
  10. Corrosion can be caused by many factors, such as the wrong type or improper application of anti-fouling paint, marine growth, stray electrical current (electrolysis), an improperly wired or damaged MerCathode, etc. These types of conditions are not covered by the warranty.
  11. If you notice signs of corrosion, contact your authorized Mercury Racing dealer to arrange for an in-the-water hull potential test. This test will help the dealer evaluate your protection level & sources of corrosion.
  12. See your owner’s manual for more information.
  13. A very informative booklet on corrosion “Marine Corrosion Protection Guide” (#90-88181301) is available from our Publications office, 920-929-5110 or through Catalog Request online.

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What is the length of the corrosion warranty?

The corrosion warranty is for three years from the original date of purchase of the complete power package for 1988 and newer Mercury Racing product that have a one-year limited product warranty. See the complete corrosion warranty under the section titled Warranties or in your owner’s manual. Protection against certain types of corrosion damage must be provided by using such systems as the Mercury Precision MerCathode system and/or galvanic isolator. These certain types of corrosion damage include damage due to stray electrical currents (on-shore power connections, nearby boats, submerged metal), etc. It is the owner’s responsibility to ensure that all necessary anti-corrosion devices are in good working order and are providing adequate protection.

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What is a MerCathode and what does it do?

The Mercury Precision MerCathode system provides automatic protection against galvanic corrosion. It is a solid-state device that operates off a boat’s 12-volt battery and provides protection by impressing a reverse blocking current that stops the destructive flow of galvanic currents. If your power package does not come already equipped with a MerCathode system, Mercury strongly recommends that you install one, particularly if your boat is equipped with a stainless steel propeller or other submerged stainless steel hardware.

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What is a galvanic isolator and what does it do?

The Mercury Precision Galvanic Isolator is a solid-state device that is series connected in line into the boat’s green safety grounding lead ahead of all grounding connections on the boat. This device functions as a filter, blocking the flow of destructive low voltage galvanic (DC) currents, but still maintaining the integrity of the safety grounding circuit. A galvanic isolator is only necessary on boats utilizing a shore power connection.

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My sterndrive paint is peeling and/or blistering. What is going on?

One of the first signs of galvanic corrosion is paint blistering (starting on sharp edges) below the waterline, with a white powdery substance forming on the exposed metal areas. As the corrosion continues, the exposed metal areas will become deeply pitted, with the metal actually being eaten away. Galvanic corrosion of aluminum sterndrive units, or any other underwater aluminum on your boat, is accelerated by attaching stainless steel components like propellers, trim planes (if connected to engine ground) and after-market teering systems. Whenever you add stainless steel accessories, it’s a good idea to have the corrosion resistance checked to make sure it is still adequate.

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Why is my stainless steel prop rusty?

Stainless steel propellers can discolor and form areas of light rust. Brushed finish stainless props are more susceptible than brightly finished stainless steel props. Rust stains can occur from polluted water, galvanic corrosion from the boat or marina, or from oxygen depletion. The propeller can be easily cleaned with rubbing compound or Scotchbrite. Do not use steel wool. After cleaning, use chrome polish to protect the finish. Stainless steel props can also turn white from calcium or lime in the water. In this case, clean the prop with household mineral bath and tile cleaner. Again, do not use steel wool. Follow-up with chrome polish to protect the finish.

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I am looking at buying a new boat which has several different engine/sterndrive options. Which one should I get?

This is a complex question which doesn’t really have a definite answer. It is similar to purchasing a new car and trying to decide which engine or transmission to get. You should look at the pros and cons of each option and decide which features are more important to you for the type of boating you intend to do. Many times, boat manufacturers will have test data available illustrating the performance of the same boat with different power options. Many dealers will be happy to arrange a test drive with different engines.

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What are the differences and advantages/comparisons between the Bravo One, and the Bravo Three sterndrives?

The Bravo One is designed to excel under the high-stress requirements of today’s performance boats. Bravo One employs heavy duty shafts and bearings coupled to precision forged gears to withstand the heavy torque and thrust loads. A smart-styled, sleek, and strong hydrodynamic gearcase slices through the water at speeds in excess of 85 mph (137 km/h) without blowout.

The state-of-the-art Bravo Three sterndrive system represents the ultimate in power for everything from runabouts to mid-size cruisers in the 40-60mph (64-97 km/h) range. The Bravo Three can provide faster acceleration, rail-like tracking through turns, and lower RPMs while cruising, to improve fuel economy. In simple terms, the Bravo Three utilizes the concept of counter rotation – two propellers turning in opposite directions – to counteract the listing some boat designs experience with a single prop sterndrive.

For enhanced performance and efficiency, all Bravo sterndrives feature a quiet, smooth-shifting steel cone clutch mechanism which provides for higher torque-carrying capacity and added durability.

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What are my choices in the Bravo Family?

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5 thoughts on “Sterndrives FAQs”

  1. I have a Mercury Racing 575 SCI w/ Bravo One XR Drive. I am experiencing about 30psi fuel pressure when I first turn on the ignition.After crancking and starting the engine,fuel pressure jumps to 55-60psi.This excessive fuel pressure seems to cause the engine to load up and stumble on idle and excelleration.

  2. I have twin 575 sci’s that have run flawlessly until this summer. They idle perfectly and run like normal, but both engines now rev to 4600 RPM and stop there. My marina has changed to 89 octane with 10% ( regular automotive gas, basically ), could it be that the computer is sensing this, and only allowing both engines to rev to this point to avoid spark knock and protect the engines ? I can think of no other reason that BOTH engines would do the exact same thing at the same time.

    1. Hi Todd,

      Your 575 SCIs have no way of detecting what type of fuel they are running on. Check your propellers to make sure they did not pick up dings, otherwise you may consider taking it into your local technician.


    2. I had the exact same issue this past summer, late season when my marina switched to 89 octane and that was all the higher mine would rev also, I came to the same conclusion that the person above did to, and was going to run octane boost this year and try not to purchase fuel from my marina again. I was told the same thing, it was preventing spark knock and protecting the engines.

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