Get a Step Up with K-Plane Trim Tabs

K-Plane trim tabs were first developed to endure the harsh environment of offshore powerboat racing.

Mercury Racing® K-Planes® have long been considered the gold standard of trim tab design, durability and performance.

Originally developed to endure the punishing rigors of offshore racing, K-Planes feature a strong, corrosion resistant aluminum casting with large support ribs for enhanced durability.

The Reasons Why More Performance Pleasure Boaters, Racers, and the Military Trust K-Planes over Competitive Brands:

  • The proven gold standard on the liquid battlefield of the offshore race circuit
  • They plane boats faster and keeps them level for a safer, smoother ride in a variety of conditions.
  • Heavy duty, corrosion resistant aluminum casting with large support ribs for unparalleled durability
  • Double-acting hydraulic trim cylinders maintain position and react immediately to fingertip control from the helm
  • Elastomer mounts on each end of the hydraulic trim cylinders dampen impact loads, eliminate free play and eliminate contact between the stainless steel pivot points for enhanced durability, trim accuracy and corrosion resistance
  • Electrically bonded components and large sacrificial anodes further protect the tabs from the corrosive salt water environment
  • Heavy-duty hydraulic trim pumps, designed specifically for K-Planes, withstand the torture of offshore power boating

Getting on Plane

Trim tabs work in-concert with outdrives when powering a boat on plane. Tucking the drives under and the tabs down forces the bow of the boat down. This brings the boat on plane quicker, without a loss of visibility. Once on plane, the operator first trims the tabs up and then trims the drives out until the most efficient running attitude is achieved.

Tabs, when put in a level position with the bottom of the hull, act as hull extensions or after planes. As a wave throws the bow up, the tabs dampen the boats reaction, leveling and smoothing the ride.

Tabs and drives should be trimmed up when operating in a follow sea. The raised bow will compensate for the waves lifting the stern. Tabs are also used to fine-tune the handling of a boat such as a catamaran that may have a gentle bounce or porpoise when accelerating to optimum running speed in mild water. In this case, the drives are set at their optimum trim.  Dropping the tabs, a touch at a time, will dissipate the porpoising while maintaining hull efficiency.

At idle, trimming tabs full down will slow boat speed, reduce the wake size and straighten the boat’s track.

Independent Actuation

Sea conditions or an unbalanced load may cause the boat to lean (or list) to one side or the other. List may occur in a quarter following sea. The waves lift the stern unevenly, causing the boat to pitch forward and roll opposite the lift. Dropping the tab opposite of the side being lifted will correct the listing for a dryer ride. Similar adjustments can be made for boats listing due to an uneven load. Bumping the tab on the heavy load side down will cause the stern on that side to lift, leveling the load.

K_Plane trim tabs feature electronic trim senders which enable the tab positions to be displayed on modern displays such as Mercury VesselView monitors.

Boats equipped with K-Plane trim tabs require a trim indicator that provides the operator an accurate, real-time reference of both drive and tab positions. SmartCraft electronic trim senders are available with 150S, 280S, and 380S K-Planes. The electronic sender provides the option of having drive and tab trim positions displayed digitally on a variety of large, easy-to-read electronic displays available from Mercury’s SmartCraft Vessel View to Simrad and other manufacturers.

Mercury Racing continues to offer a full array of mechanical trim indicators first developed by Kiekhaefer Aeromarine for use with sterndrives, outboards and K-Plane Trim Tabs.


The 380S K-Plane in Hulkin’ Green.

Custom color options enable boaters to color match the tabs to boat graphics and color optioned Mercury Racing M6 M8 sterndrives.

Available for boats 21-feet and longer, K-Planes are available for outboard and sterndrive raceboats, performance boats, center consoles, commercial, and government applications.

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23 thoughts on “Get a Step Up with K-Plane Trim Tabs”

  1. I have model 110 k planes, are there any parts available for repair? Is there a new model number that kept similar dimensions as the 110s?

    1. Hi Dave:
      We no longer produce the 110S K-Planes. The closest model in size would be the 150S K-Planes; part number 841944A02. Retail pricing for the set is $3422.98 The tab itself is 11.6″ in length and 11.5″ wide. The backing plate is 14″ wide. They are for 21-foot to 30 foot boats. They feature digital trim senders for use with Mercury’s touch screen VesselView monitors.

  2. Hi,
    Need the Part #’s to convert Mechanical Senders on 380S K Planes on 06 Fountain…. Not having VesselView now, Would need a 2 Row Digital Display that would receive from the new senders….which I believe you also make…(I think Gaffrig and Latham also make these)

    1. Hi Mark:
      What style – year K-Planes do you have? Do they have the Kiekhaefer logo or Mercury M logo? I you have the former; thery can’t be updated. Unfortunately, a kit does not exist for the newer planes and thus you would need to order the individual parts.

  3. I have 380s planes with digital sending but the plug does not seem to have place to go on my Vessel View 7 harness but there was one on the old harness for the SC5000 System View that was in place prior. How do I make this work?

    1. Hi David;
      What engines do you have? You can plug the digital tabs into the transom harness (if it had the connectors) or into a tab module. Does this help?

  4. Hi, I have a 2001 wellcraft scarab sport 302 with twin yamaha 250’s on a Stainless Marine 36″ Motor bracket. I think i want the 380S Kplanes over the 280S. Which ones would you all recommend?

    1. Hi Ferdi:

      I think the 380S would be overkill. You cold actually go with the 150S K-Planes. They are good for 21-foot to 30-foot boats. The 150S part number is 841944A02. The 280S is another option; they would be more than enough. they are desfgiend for use on 21-foot to 30-foot boats as well. And they are available in custom colors. The 280S part number is 842768A05.

      Click here for additional information.

  5. I have a Boston Whaler 320 Vantage on order with 2 400r’s. I have included the autotrim option on the build. I assume they are using a conventional trim tab. Is it feasible to interface K Planes with this package?

  6. I have 280s k-planes with the Kiekhaefer logo. Can I buy a replacement transom plate for these tabs? Can I retro-fit the new version of the transom plates by using the new upper shaft for the hydraulic piston?

  7. I have a 38 fountain with those k-planes I need to replace both of the cylinders but those are 28 inch long, are those livorsi?

    1. Jose,

      Do your K Planes have an “M” or a “K” stamped on them? That is new vs old style, with the year break around 2005.


  8. I have a set of 2003 380’s with a “K” on them and they need new upper plates that mount to the transom. Looks like the original plates are NLA. Aside from the Smartcraft sender mount on the current upper plates, are the mounting holes and ram mounts in the same location? Looking to install these and still use mechanical indicators. Thanks

    1. Steve,

      Mounting holes are all the same, but the other big difference is the hinge pin is 5/8″ on the new style and 1/2″ on the old style.


  9. is there a kit to convert from a “K” logo to an “M” logo bottom plate only? just want to buy new longer bottom plates and use all of the other parts.

    1. Frank,

      Most guys use the 3M 4200. It creates a great seal and you will still be able to remove them if needed down the road.


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