I am running a 1542 Grizzly with a 27 HP Kohler GoDevil Longtail and getting about 16 mph with 2 guys and a pretty good amount of gear. I have ordered a tiny tach to see how many rpms I am running but I don't think I am getting as many as I should be getting. I have read that the motor should run just below the surface for the most speed. How do I know from looking in the water if I am running about where I should be or if I need to start messing with the cavitation plate?

Thanks for the help.

Don't know how much you guys weigh or what you consider to be a "pretty good amount of gear" but 16 mph sounds pretty good for your set up. While your running full out take your hand off the handle and see if the motor stays at the same depth. When your cavitation plate is at the proper angle it should maintain the same depth. If your prop keeps popping out of the water then you need to bend the cav plate.

If its sinking to deep, bend the cav plate downwards. if its sitting to high bend it up.

Can somone post a pic of how much to bend it?


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I would start by bending only 1/4" at a time and check your planing depth. I never had to do it on my two GD's an 18 and then a 25 HP. My current MB 27 longtail has a "trim tab" on the trailing edge of the cavitation plate- it is rectangular steel, 5 3/4" x 2 1/4", held on by three bolts; bending this achieves the same effect and then you don't have to mess with the cavitation plate itself. I don't see why this tab could not be put on the GD cavitation plate. I have noticed with each prop change that I've made, I've also had to slightly adjust the trim tab.

Thanks for the help guys. I bent it a little and it was too much so I bent it back down a bit and it seems to be about the right depth now.

I suggest you download the manual from the GoDevil website. It gives a very good explanation with pictures of exactly how to do it.

I did it yesterday. My speed stayed the same, and now it is a lot easier to operate.

Glad to hear that, swamprat. Greetings, stualaska! I know you ran a longtail up there for some years, and you are running a GD surface drive now? Does that surface drive have a cavitation plate? On the GD site the pictures display that feature, unlike some other mfg.'s of surface drives that do not have it. I know you can electric or manual trim the motor but do you need to also trim the plate? I believe I also see a bendable trim on the bottom skeg, perhaps to adjust right/left steering? Are there areas up there where a longtails are still running? This weekend we are just finishing our first phase of nine days of duck hunting- I've bagged limits of ringbills every day, but after seven straight hunts I am taking the weekend off. Did not mean to hijack this thread BW, just wanted to say hello to Stu!