Engine slows when cover installed

[artherm]

My Evinrude 9.5hp, 1967 model has developed a problem of running fine when the cover is removed, but slows when I install it. I thought maybe the foam in the cover was snuffing out the carb, so I removed some around the top mount carb. No change. Any ideas?

 

[tashasdaddy]

Re: Engine slows when cover installed

the gasket between the powerhead, and exhaust housing, or the one on top of the impeller. with the cover on it's breathing exhaust, low oxygen level.

 

[Xcusme]

Re: Engine slows when cover installed

Sounds like you have a leaky exhaust gasket pumping exhaust into the cowling, choking off fresh air to the carb. Replace the gasket and you'll be back on the good foot.

EDIT: HA! i HAVE TO LEARN TO TYPE FASTER !!

 

[grid]

Re: Engine slows when cover installed

If you use this engine in salt water, you'll find attempting to replace the donut gasket separating the exhaust housing from the powerhead an exercise in futiility, as bolts break, etc. The engine was designed to self-destruct unless factory engineers worked on it. Having seen your problem a bazillion times, I ended up drilling holes in the aft of the engine cover, under the hand-hold, to help draw the exhaust out. Worked pretty well for the cost~~

 

[F_R]

Re: Engine slows when cover installed

I assume you are talking about while running on a boat? They won't run worth a hoot in a barrel with the hood on.

There are two main exhaust leak areas. Well 3 actually.

1. Does the exhaust sound noisy with the hood off? They have a habit of corroding a hole through the bottom of the exhaust manifold (out of sight, sort of forward of the bellows hose)

2. Has the lower unit been removed for anything like a water pump job? There is a rubber seal that goes on top of the water pump housing. If that seal is left out it will fill the hood with smoke and smother it.

3. There is a rubber bellows seal on the shift rod about half way down in the midsection. You can't see it, but it's in there. It is very flimsy stuff and when it deteriates and rips, smoke will also go up through there and smother the motor.

4. The big rubber flap around the midsection gets most of the blame, but probably is the least of the offenders. If it truly is bad or missing, it will contribute to the smoke problem mostly at idle whien the boat is more or less at a standstill and exhaust is bubbling up around it. At any speed, that smoke is left behind in the wake.