787 bogging in water not on trailer

[simy200]

Hello guys, thanks in advance for your time and help.
I have a gtx 1996 787 engine with dual carb.
After an 2 hours ride the engine stop. Get out of the lake an notice a hole in the exaust that was leaking water from, repair the hole with aluminium soldering.
try on the trailer and work perfectly. Take to the lake , hard to start and impossible to rev up more tan 2000 rpm, and ski smoke a lot from behind. Hard to idle and stop by itself at idle. Back on the trailer at the house 5 minutes later, start easily and run great, get full rpm and no smoke.
my hose gaz are new, carb have been rebuild this spring, spark plug are new, compression is good in both.
Someone have any idea whats can cause that.
thanks a lot

 

[GGuillot]

Carbs rebuilt with genuine oem kits? what's the compression numbers?

 

[etemplet]

Makes me think that water is getting to someplace it should not. Are you sure the hoses are connected properly.

 

[simy200]

Thanks both of you for youre time.
Yes I rebuild it with genuine carb parts.
not sure why some hose can be interchange somewhere, its run great for few hours and sudenly it get worse...This is why i’m questionning myself and take more info from other that may have easy solution.

 

[simy200]

Do you guys think that it can run great on trailer whitout water or load and in water they run not god at all, it can be cause by a pad carb setting or something lime that? I’m realy confuse to make adjustements or setting if they run great outside of the water?

 

[mikidymac]

Running on the trailer will tell you absolutely nothing since there is no load on the engine.

 

[simy200]

I got 150 on each side.
I do I know if my wear ring is due, can I turn the impeller or turbine by hand to se if its free and easy to spin? Can it be the water flow goes to ghe engine?
I would give a try with my garden hose tomorow.
Thanks again all of you for your time

 

[sharky300]

I am having the same problem on 1992 xp... I do not have the answer, but some research I have done (google) suggest it can be excessive wear on the rotary valve... I have been trying to do more looking, but may order it up, just to see if works... I can’t find anymore info. Will be a week or so, but if it works, I’ll be back....

 

[WaterJet]

You could be leaking exhaust gas into the engine bay if you didn’t install the pipe properly after welding it. That would caused reduced rpm.

 

[simy200]

Finaly.... Trouble is gone. I’m very shy to tell you my cause. 1 spark plug was blow. Why ? I dont know, but now its run perfect...
Thanks again all of you for your help and time.
And yes , always check plug first on 2 strokes...

 

[Joser4200]

Makes me think that water is getting to someplace it should not. Are you sure the hoses are connected properly.

So I figured out what the problem was so I guess when the rings shatter in the cylinder they stay inside the crankcase I’m new to this 2 stroke stuff I was tarring into today and my brand new piston had chunks of metal ding in it and the head dings in it also pissed now I have to rebuild the whole engine