exhaust leak 1991 90hp

[zimmer62]

Alright, I'm 99% certain my problem is an exhaust leak. The engine will stall at low low rpm, but only if the engine cover is on.... with the cover off, the engine runs great. At high RPM it's great and isn't a problem... (I'm assuming thats because I'm moving pretty fast at that time, clearing out the housing of any exhaust fumes)

My question is what am I looking for, and whats the easiest way to go about fixing it. I rebuilt the motor last summer, and I suspect it's either a seal, or a gasket, but I really don't want to tear the whole thing apart if I don't have to. I thought about venting cover with a intake vent, but before I do anything stupid and blow it up I thought I'd check out the forums... thus finding out it'll probably screw up the fuel air mixture and melt my pistons... so scratch that idea.

When putting the powerhead back on there was some high temp rtv sealant used just before putting the powerhead on, that went between a couple surfaces... If I waited to long to get the powerhead on and bolted, it's possible for the RTV to dry a little, could this be my problem, that it wasn't wet and adhere to both sides?

I'm really looking for a way to avoid tearing it all down and finding out that didn't fix it, so if you have any tips to find the source of a leak that would be really helpful.

 

[zimmer62]

Re: exhaust leak 1991 90hp

anyone?

 

[roscoe]

Re: exhaust leak 1991 90hp

If there are no leaks up top anywhere, the only place left is under the powerhead itself, or the exhaust tube in the mid section.


Running with the cover off, or putting air vents into it, will not damage your motor.
The fuel air mixture is controlled by the carburetor.

 

[fab9racing]

Re: exhaust leak 1991 90hp

so i am to assume that you think that the air the motor is getting in is contaminated , thus causing you to have a poor idle, lets try this get you a timing light and hook it up to a plug wire and while the boat is in the water with the motor tilted down take the covers off the carbs and watch the fuel pattern of the carbs this is a easy way to see if your main jet is bleeding,

 

[azlakes]

Re: exhaust leak 1991 90hp

... hey there Zimm;

I had a similar problem and asked for some help and got this response. Check your 'belows' if you have one before a powerhead tear down.

Hope it helps you some.

Hi Frank,

Question. There is a rubber boot between the lower leg housing and two water pump spurt holes that has a leak and small drip. Its held on by a metal squeeze ring and thats it. Is it easy to replace and ok to run with a small drip until replaced? Any tricks to get this on when I buy a new one?

Thanks for any tips!

If it has a hole and is leaking then you want to replace it because it is the idle relief . when the engine is sitting low in the water, exhaust gases pass through it. If the leak gets bad, the exhaust will stall the engine with the hood on. With it off, the engine will run normally.
However, if it is leaking where it enters the rear shroud, then it might just be mis-aligned. It is spring loaded inside and that is what holds it firmly in the tapered seat. Reach down and wigge it back in. The end of the plug is tapered to match the seat.
If you need to replace it and can't get the clamp off with a pliers, then you will need to remove the rear shroud to get to the clamp.Six screws on the front of the shroud and usually six inside the engine. When I replace the bellows, I use a plastic zip tie or a stainless screw clamp--much better than original.

Oh, yeah. before you buy a bellows, check the old one. Inside the tapered end is a plastic sleeve that the internal spring bears against. Sometimes the sleeve distorts ,not allowing the bellows to seat.