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  1. #1

    Yamaha GP800, any tips on how to keep this thing in the water?

    I have a Yamaha GP800, the ski runs pretty good but in even the lightest chop it will start porpoising really badly. As far as I know everything is stock. The main issue is that at the Lake of the Ozarks its usually pretty choppy and this thing does not seem to handle it all that well. Are there any tricks or modifications that can be done to help smooth out the ride a bit?

    I also seem to have a hell of a time getting it started when its been sitting for a week. Once I get it started then it starts right up the rest of the weekend. Is this typical of a 2-stroke or is there something that could be causing it to not fire up? Have to crank it over and over many times and eventually it fires up, just about the time the battery is about dead.

    Lastly, any fairly inexpensive performance modifications out there that can be done to this ski? I also have a 2012 SeaDoo RXPX that we take out together across the lake, problem is that my wife can't keep up on the Gp800 and I get in trouble for not slowing down for her.


  2. #2
    Quote Originally Posted by Dragunov View Post
    I have a Yamaha GP800, the ski runs pretty good but in even the lightest chop it will start porpoising really badly. As far as I know everything is stock. The main issue is that at the Lake of the Ozarks its usually pretty choppy and this thing does not seem to handle it all that well. Are there any tricks or modifications that can be done to help smooth out the ride a bit?

    I also seem to have a hell of a time getting it started when its been sitting for a week. Once I get it started then it starts right up the rest of the weekend. Is this typical of a 2-stroke or is there something that could be causing it to not fire up? Have to crank it over and over many times and eventually it fires up, just about the time the battery is about dead.

    Lastly, any fairly inexpensive performance modifications out there that can be done to this ski? I also have a 2012 SeaDoo RXPX that we take out together across the lake, problem is that my wife can't keep up on the Gp800 and I get in trouble for not slowing down for her.

    Even tho the power to hull weight on that ski (gp760/gp800) is in your favour, it had design flaws in the hull. Do a search there are tons of info on that. Esentially you will need to at least shim the ride plate in the rear using ss washers to keep the nose down. Riva also made trim tabs for it and adjustable sponsons that help when adjusting them down in the back. The stock one's are adjustable too. Tho hard to find, much of that stuff is still available on ebay. Protec also still has some stuff like ride plates, heads, F/A's, etc.

    That boat won some awards back in the day and the 800 motor puts out great power for a twin. R&D and Group K still has motor mods/kits for it. But the easiest thing to do in the way of increase performance is F/A's, shaved or aftermarket heads, and taller prop. The good news is that the twin is easy to work on... .

    On trick on the starting procedure you can try is crank it for about10sec long enough to energize the pv's and fuel pump, then with it off pump the throttle several times then re-start.
    Good luck and have fun.

    PS: by the way, have you checked your compression (starting problem)?

  3. #3
    I have the same issue on my 2000 Yamaha GP800. I just bought a 1997 GP1200 ride plate as it's longer than my factory piece. they said the longer ride plate helps and then start with two SS washers on each rear bolt and either add or subtract to get it right.
    I also have the factory adjustable sponsons on mine and have them adjusted all the way down and when the water is calm the machine handles like it's on rails but any sort of chop and it porpoises.

    you can pick up a stock 97 gp1200 ride plate on eBay for $30-$40. I just paid $35 shipped for one that looks to be in great condition. also stay away from the Riva "Groovy" ride plates as everything I've read is that they make it worse. most people I've read about either go with the factory 97 gp1200 plate or get an R&D plate and shim it from there. I decided to get a factory piece vs spending triple the money on an aftermarket plate.

    I've also read to get an aftermarket intake grate which would help scoop water and keep it full vs sucking in air. but I'm going to try the ride plate first and see how well that works before spending $150+ on an intake grate.

    as as far as trim tabs go, I haven't had any luck finding any in my searches and nobody makes them anymore for the GP800.

  4. #4
    Thanks for the advice, I will start looking on ebay for a ride plate. As far as compression, no it has not been checked. When we get the thing to start it runs like a dream, but that first start can be a real challenge after it has sat for a week or 2.

  5. #5
    Myself's Avatar
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    You better check to see if the power valve keepers have been upgraded.

  6. #6
    OzarkYamMonster's Avatar
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    Hey Dragunov, where do live or ride @ the Lake ?

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