96 speedster engine problem

[Booost90]

Hey guys...first post here:cheers:

I was out on the lake today and ran into a problem with one of the 787 motors in my boat. Everything was good and running fine, and then the motor cut out. It will start back up fine, idle, and run at a low rpm, however with any kind of load the engine shakes more than it should, and then slowly tries to die until I back it back off to idle. I limped the boat to the dock, and once I got home I hooked the hose up to the motor that is having problems and ran it in my driveway....it seems to be spitting out a lot of dirty oily water. The good motor is spitting out clean water. Does anyone have any idea's what this could be? I plan to take the boat in this week and have it diagnosed if I happen to not get a response. If there is anything you recommend I check...i'm all for it (i'm pretty mechanically inclined).

Thanks!

 

[JPX]

Blown exhaust gasket? Water cooled jacket on the outside of the exhaust pipe might be getting exhaust pushed into the cooling loop.

 

[Booost90]

wow that was quick. I will definately have to check that out.

Thanks

 

[Booost90]

Ok...I just looked around a little to double check. Is this the exhaust gasket?

 

[Booost90]

Ok...I just ran out and did a compression test. Each cylinder is right at 130, maybe a tad more in one of them. There is oil on the spark plugs though...

 

[JPX]

That's the gasket I was thinking of. Here is what it looks like on the inside:


Water flows through the outer two ports - exhaust through the center port. If the gasket fails or the exhaust pipe has loosened from the manifold (bolts and nuts shake off or the pipe casting cracks), then you will have exhaust and water mixing where they should not be.

 

[Booost90]

Alright awesome. I did notice when I took it off that the bolts were not very tight

 

[JPX]

I went out and took off my purple exhaust pipe from my 96 speedster to check the gasket, and the bottom half of the pipe just fell right out of the clamps as if it was real loose. Here is a picture to show you what just fell out...it is the green circle. http://i32.photobucket.com/albums/d2...g?t=1215474613

That sounds like the problem then. Exhaust gas is probably getting pressured into the water loop. When an imbalance in exhaust exists, the engine will run poorly and invite water under certain conditions into the cylinders. With poor combustion, the fuel/oil mix ends up spitting out of the water outlet out back.

I used copper silicone head gasket sealant for the exhaust manifold gasket surface (both sides) and blue Loctite on the bolt/stud threads. 2-strokes naturally vibrate a lot and this point is very sensitive to loosening up.

My HX actually cracked the pipe all the way open and flooded the boat - I was stranded in the middle of San Luis Reservoir half submerged in the water for over an hour before the ranger could pick me up because of that damn thing. Cost was covered by 3 year extended warranty. Of late, the second pipe has corroded at one of the end caps and sprung an external water leak.


I'd suggest also checking the other engine's pipe - may find that it is actually tight. But if any hardware is loosening up, then you'll end up having the same problem there too.

Overall poor running conditions point to fuel delivery - most likely stemming from clogged internal filters to the carbs. My sig link below will help you walk through that project.