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  1. #1

    GP 1200 diagnosis help

    98 GP 1200. My second summer to own it.
    I was out testing the new aquavein intake grate on the river today, and everything was going great. Few hours later the ski started to hesitate a little after i would let off the throttle and then open her back up. Slowly the hesitation turned into sluggishness, for instance it would take a little longer to get to top speed and it just felt strained. That led to missing and it would have a hard time getting over 45 mph, so i immediately took it in and loaded it up once that started happening. Didn't want it dying on me..
    With that said, this was my second ride of the summer and it ran totally fine for a good while before it started having trouble.
    I've already got the spark plugs out and air box opened up (though i don't know what to look for). I noticed alot of excess oil in the air box so much that some leaked out and gathered in the bottom of the hull, also noticed little specs of trash in air box.
    I'm not a mechanic but i suspect it has something to do with the carbs or spark plugs... New plugs? Spray some carb cleaner in carbs?

    ANY suggestions guys?

  2. #2


    You might have a reed going out. Once they start to crack it will blowback thru the carbs because the reed is not sealing as it should.

    One test is to hold your hand over the carb while you crank it over. Dont start it just crank it. You should feel suchion but if you feel blowback its the reeds.

  3. #3
    I gave that a try and i didn't feel any blowback, each of the three carbs created suction. Guess the reeds are alright.

  4. #4
    Changed the plugs and it ran like a top. Problem solved

  5. #5
    Budman's Avatar
    Join Date
    Jul 2008
    If you have oil in the bottom of your hull you may have a bad oil line. These gp's are notorious for having the oil lines crack or come off. If your not getting good oil flow to all the carbs the engine will tighten up and start to run crappy. Eventually it will ruin the engine. I was lucky. When I started feeling the engine get sluggish I saw oil in the hull right away. I found the bad oil line before any damage was done. Get a mirror and a bright light and inspect the lines. They should be replaced and good clamps installed. Or go to premix like I did.

  6. #6
    I did check the oil lines and they are tight, i didn't find any evidence that they were leaking anywhere. The air box seems to be filling up with oil and that oil is leaking out into the hull and settles in the bottom... Is this normal? Also i have been wondering about going premix, what specific modifications would i have to make in order to convert to premix?

  7. #7
    Budman's Avatar
    Join Date
    Jul 2008
    The only mod that has to be done is to remove the oil pump and install an oil pump block off plate. The plate is only about 20 bucks. Then you will have to buy some fuel jugs and a ratio rite measuring cup. The best place I have found to buy good jugs is . I mix mine at 40:1 and it runs great. There is a lot less smoke with amsoil synthetic.


  8. #8
    Thanks Budman. Sounds simple enough.

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