1997 gp1200 engine, mods and general questions

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  1. #1
    PWCToday Newbie
    Join Date
    Aug 2018

    1997 gp1200 engine, mods and general questions

    Newbie here so lots of questions. I'm trying to understand whether the "R" at the end of gp1200R means power valve. I just bought a 1997 gp 1200 with a blown engine. My jet skis guy is putting in a new engine. I am assuming the blown engine is a non-power valve engine.
    First question: When replacing a non-powervalve engine is it a must to replace with another non-powervalve or are they interchangeable. From what I am reading I am guessing they are not compatible.

    I also want to have my mechanics do some modifications that will get the best bang for the buck as far as top speed goes. Everything I am reading is for modifications for the GP1200R. what are the best low cost modifications for a 1997 gp 1200 non powervalve to get the most speed out of it. What is a reasonable speed to expect for the stock vs. a modified. Thanks in advance for helping me understand all this!!

  2. #2
    PWCToday.com Is My Home Away From Home Myself's Avatar
    Join Date
    Jun 2006

    Re: 1997 gp1200 engine, mods and general questions

    The 97-99 gp1200 are non powervalve models. Commonly referred to as 65u. There are very rarely any "low cost" mods in the PWC world. These machines will run 57+ mph in stock form. They are also known for porpoising badly. Being a '97 yours will have plastic trim tabs on the hull, rear bottom. They are commonly broken or missing. Replace them with aluminum and make them an inch longer. If your ride plate stops at the rear of the hull, you'll want the longer version. A "scoop" type intake grate is also an excellent mod. You can also lower your sponsons and adjust the twist trim system to get as much downward angle as you can. All the above will help just to make the ski rideable at speed. There is a preferred Skat Trak impeller but I can't remember which pitch. You can get a bunch more power from porting and head work but not on a new engine, it will void your warranty. If your mechanic does not know about the balanced return mod for this engine setup he needs to figure it out. Reliability is increased 3fold.

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

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