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  1. #1

    98 gp1200 porpoising

    i just bought a 98 yamaha gp1200 and after 35 mph it starts porpoising , what should i do to fix this problem , im new to the pwc world. Thanskss

  2. #2
    Join Date
    Apr 2006
    Orange, TX
    You have a few options. You need to ditch the short stock ride plate. The 97 stock plate was longer, or get a shredmaster. You can try shimming the rear of the plate down, but you need a longer plate. Also, you need trim tabs.

  3. #3
    Dave Sharp dav_dman's Avatar
    Join Date
    Aug 2005
    louisville Ky/so. IN
    short plate came in 99.. he should be good to go if he just takes your advice and shims the rear bolts 1/2". With no trim tab work , or spons work, or grate work, or swapping for the zero degree nozzle.. i suggest a full 1/2" down on the back of the plate. With that other stuff you only need about 30-60 thou shim.

  4. #4
    would it slow the ski a little if i shim it 1/2 inch??

  5. #5
    cfgp927's Avatar
    Join Date
    Dec 2005
    Warsaw, Missouri
    You'll scrub some top speed with the rear of the plate shimmed down...but not as much as the porpoising is costing you now! Start with the plate and then look at the other items in the equation. What kind of water do you normally ride in? Glass, light ripple, heavy boat chop, etc....depending on what water conditions you ride in, will determine your ultimate set-up.

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