“Step right up!”

A favorite of the Mercury Racing stable, our 525 EFI. Its stout components make it a tempting target for upgrades.

There are “tuners” out there that offer supercharger kits for Mercury Racing 525 EFI engines (and others). Some of these kits reportedly boost horsepower and torque as much as 50 percent. They reprogram our engine controller to override its logic and limits. Yes, there is more power to be had – for a time. We program our ECUs to keep engines within their physical limits and offer good power with reasonable reliability and durability.

Ah, the joy of performance on the water! This 525 Bravo One XR powered Nordic is a great running and reliable combination.

One tuner just offered a “price reduction.” Their claim is to make power upgrades more affordable. Beware of the sales pitch, “Step right up! It’s on sale!” Alarm bells should be ringing in your head when you hear those words. If you’re tempted by that offer (and your warranty has expired), please proceed with your eyes wide open because just the opposite is the likely result. Here’s why “affordable” may prove very expensive.

Powered within its design limits, and with proper maintenance, our Bravo One XR is a robust drive.

A 50% boost in power and torque, if true, would put a 525 between 785 and 795 hp. Our engines are tough, but they are not designed to operate at these power levels, nor at a higher RPM “red line.” And IF a modified engine survives, its torque output would be well beyond the capacity of any Bravo drive. BOOM! Instant, unhappy boater. More “Gee, I was just driving my boat at cruise and the damned Bravo…” (It seems the drive always gets the blame even when the engine is modified beyond drive capacity.) This makes me crazy. We develop engine and drive-lines as a system – matched to live together – and warranted because they do.

Our 700 SCi engines packaged with dry-sump NXT1 drives are both fast and reliable. Mercury’s extensive development and proprietary components have made this the most reliable supercharger of its type in the industry.

Racing limits the Bravo XR to 600 hp so consumers have a good experience. At 662, our engineering technicians can break Bravo XR drives almost at will. That is why 662s and 700s come with NXT drives and warranties. We believe people should know what they’re getting into and get the value they pay for. If you want more power, buy a boat or re-power with a matched engine/drive package. Then you get dependability, not frustration, embarrassment and unexpected expense. Our goal is to keep you enjoying the water. We don’t want you driven (or pulled) from it.

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24 thoughts on ““Step right up!””

  1. Hi guys. My 525 has 100 hours on it. I am looking to tune my ecu. Do you guys do this? If so what kind of hp can I gain by doing so safely? Thankyou

    1. Hi Sean. Sorry, we do not provide any tuning services for existing or NLA products. Your 525 has low hours on it. It is a strong and reliable engine. You will enjoy hundreds of hours on the water if you run it as is.


    1. Hi Barry:

      You will want to use our Mercury Racing 25W-50 4-Stroke oil; part number 92-8M0078014. You can read he blog post I wrote regarding it here.


  2. Which oil should I use in my 190 hp mercrusier V 6 Chevy 4.3 L engine serial #L623666? This is in 2000 Crownline 18 BR. The best I can tell the engine is between a 1998 & a 2000 vintage. The boat was used one season when I bought it. I have always used Quicksilver 25W-40 oil and Merc. Filters. Many seasons I was only able to get on the water twice for the hole summer. I live in Ohio and spent way to much time at work. Retired now and hope to catch up. I am sure there are low hours for this vintage. Have read several articles about the new semi-synthetic blend. I do not to create problems and can’t afford to replace the outfit.

  3. Just read your post about what happens when you wring more out of the 525s (I’m running a pair with ZRs, 440 hrs never been touched inside). I’m a 35 year veteran engineer in the aerospace industry and get so tired of guys crying about busting up and XR even though they’re pushing 800 hp through it. Like you said….if you want to go faster open your wallet and get the next step up in hardware rather than try to make hardware do what it was never intended to do! Good job guys.

  4. Hi Rick, Running a single 2012 Merc525 in a B&H Performance Boat. We are just shy of 600hours and have taking this thing all over the country. It has been very impressive and we have followed the suggest pm schedule exactly. Over the weekend we just replaced the rockers, (2nd set)springs, retainer & locks. Lifters were replaced at 371hrs and currently setting at 590hrs. We have exensive leak down and compression test over the life. How long can we expect our 525 to live? Any extra maint issues to seek? Thanks, Steve/Liquid Marine Performance Boats

  5. Hi Rick ,
    I recently purchased a beautiful 2005 29 Fountain Fever with a 525 EFI , current prop is a bravo 16″ 29 p four blade is this the correct prop for this boat , was thinking of going to Max 5 but not sure of what pitch to use. I am currently running between 72 and 74 mph on GPS on fresh water.
    Thanks for any help Bill Mills

    1. Hi Bill:
      If you don’t mind, I suggest you submit your question to our Performance Propeller Manager Scott Reichow.

  6. Rick,
    I did speak to Scott and he recommended the Max 5 prop, just put it on the boat and we ran 76–77 mph not bad at all anything else in mind to hit that 80 mph mark , that would make my day. Definitely don’t want to do anything to jeopardize the reliability we currently have.
    Thanks again Bill Mills

  7. Hi, I have a 2003 Fountain 27 with a 2008 525 EFI. It has about 280 hours on it. I need to refresh the top-end; springs, retainers, seals and locks. What parts does Mercury use in this refresh? I would like to to keep it stock.Thanks for any help here.

    1. Hello Thomas.
      We do not refresh any of the 502 cu.in. (8.2L) based product here. You can bring it to any authorized Mercury MerCruiser dealer to have it refreshed. They will be replacing the parts with authorized Mercury Racing components.

  8. I have a 2006 Cobalt 343 with twin 525’s. I’m looking to add Vessel View and was wondering if these motors are NEMA 2000 ready

    1. Hi Kevin
      Your 2006 525 is SmartCraft compatible. We have NEMA 2000 compatibility via our gateways (module, MercMonitor or VesselView Link). There may not be any SmartCraft backbone installed from the engine to the helm so there is that aspect to consider. You will need to connect a blue data cable (with one termination resistor) from the 10 pin connector on the engine and run it to the helm. You may need a termination resistor (depends if there is one on the engine and if it can be reused) and probably a 4-way junction box. I hope this helps.

  9. Rick I am looking to purchase a used Donzi 38ZR ,staggered 525EFI’s. The drives are Bravo XR. What is the normal life expectancy of these engines? It appears 300hrs on the valve train is about average, is that correct. When is the bottom end a potential problem? What is the life expectancy of the drives? It appears most have been rebuilt with less than 300 hours as well. Are there upgradable parts that would give longer durations? What should I expect under normal use. Keep in mind I don’t run my stuff hard, however they are used boats and I cant speak for prior owners.

    1. Tom,

      Sorry for the delay in response, Rick is no longer with the company. 300-400 hrs is typical for valve train depending on how hard you run them. After that, we recommend a leak down test every 100 hours and complete rebuild at 1000 hrs. I hope this helps.


  10. Hello,

    I have a pair of 1999 Gen VI Mercury Racing 525-SC carbureted motors with about 350 hours on them and wanting to rebuild. They are in front of Bravo XR drives, which are good for around 600HP.

    In the rebuild, I’m wanting to upgrade the power output to match the capability of the drives, and thinking I definitely need new cams, maybe new heads, and maybe larger blowers, but not sure about the latter two items.

    Also, are the existing pistons & rods okay spinning to 6.000 RPMs?

    The current setup indicates an operating range of 4,800 to 5,200 RPM, and in a rebuild, my goal is 6,000 RPM, which puts the piston speed at 4,000 feet per minute; a good bit faster than 3,466 FPM @ 5,200 RPM.

    Should I plan on changing the pistons and/or rods too?

    I’m a staunch Merc Racing parts fan, so advice and part numbers would help.

    Thank you.

    1. Gary,

      We have not done any testing on that engine in excess of 5250 rpm, so unfortunately I am unable to give advise on whether or not the internals can take it. A good guy to talk to would be Bob Teague at Teague Custom Marine.


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