'99 GP800 with on-water only problem continued - PWC Forum: The best hang-out for Personal WaterCraft enthusiasts
 
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post #1 of 5 (permalink) Old 08-04-2019, 04:33 PM Thread Starter
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'99 GP800 with on-water only problem continued

I have posted about this ski before and have had two service shops work on it. There is a perplexing issue with it that must have a known solution. So far I have had new pistons installed and the carbs rebuilt. Reeds were clean. A missing flame arrestor involved with the air intake was replaced. Gas lines are fine. Power valves were replaced and Waveater clips installed. The problem is that the engine purrs on the trailer and runs immediately up to 8k rpms. But on the water, the engine bogs around 4500/5000 rpm and sounds like it is surging up and down when the throttle is opened up. Periodically, it will start to accelerate and then will launch into WOT status (with the throttle set at WOT). It was too choppy today to let it run up to max speed, so I don't know what would happen on flat water. For about an hour, the 'rooster tail' jet was working fine, then I noticed at the end of the day, there was no water coming out of the jet orifice on the rear deck. What the heck does that mean?

So this problem only happens under load. I have not pulled the impeller. I understand that a total impeller failure would allow the engine to rev up without moving the ski in the water. But would a partial problem with the impeller or wear ring that was somehow intermittent cause this problem? A drive shaft problem? What could cause gas or carb problems only under load?

The last service guy filled the oil tank and said it should work. I did notice the oil in the tank was down about an inch today, so the oil pump and oil line seem to be fine. I have been running pre-mix as well, but will no longer do this after this gas tank is finished and I replace the no doubt fouled plugs.

Is there anyone in southern or eastern Connecticut that I could talk to about this? It seems as if I am one fix away from having a ski that works very well. Thank you in advance. Peter
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post #2 of 5 (permalink) Old 08-04-2019, 08:16 PM
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Have you tried leaving it strapped to the trailer and backing it into water with the seat off it. Start it up and run it up through the rpm a bit at a time watch the power valve cam. It should start opening when you get to about 6000 and be full open around 6500. Due this several times till you know the valves are working consistently. Note what the valves are doing when the motor acts up. Are the valves stuttering. (Trying to open and then closes)
The surging your talking of leads me to believe its a lean carberation issue though.
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post #3 of 5 (permalink) Old 08-05-2019, 08:46 AM Thread Starter
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I will do this next. Thank you Dave. Any idea what happened to the rooster tail jet?
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post #4 of 5 (permalink) Old 08-05-2019, 12:00 PM
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Quote:
Originally Posted by Peebs View Post
I will do this next. Thank you Dave. Any idea what happened to the rooster tail jet?
It comes from a hose off of the jet pump. Look under the rear of your ski for a loose or broken hose in that location
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post #5 of 5 (permalink) Old 09-21-2019, 11:44 AM Thread Starter
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OP here. I thought I would let you know what happened next. I took my GP 800 to a third service shop where they seemed to know what they were doing. I explained the problem. The tech took the ski out the next day and found the problem existed as stated. They went through from the carb side and from the exhaust side and determined that it was most likely a carburetor issue, as Dave suggested. They rebuilt the (rebuilt) carb and tested it on water. Said it ran fine.

I took it out yesterday and in the harbor I regularly got the speed up to 35 mph before I ran out of water. It was too choppy to get outside the harbor. I will take it out again today, but I think the problem has been solved and I have a solid 20 year old ski.

The only thing I noticed yesterday is that sometimes there seems to be some hesitation around 5000 rpms, which is where the valves start to open. After a few seconds, rpms and speed increase rapidly. Thanks again Dave (and Rods).
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