Carb intake and exhaust

I know nothing about 2-strokes, and less about boats.
It's a 1969 40 HP. I have lots of ways exhaust is coming into the engine cover area. It will only run w/ the cover off. I expect it's because there is so much exhause in there. How does the fresh air get to the intake? The cover pretty well seals everything. Am I supposed to have a filter/ intake tube on the inlet side of the choke?
Lost and confused

Re: Carb intake and exhaust

You probably have a bad exhaust housing gasket (gasket between power head and exhaust housing). As for air in-take, I think your '69 is much the same as my '71. Just below the carb you should see a round chrome looking disc about 5 inches in diameter. Air comes in from under it.

Re: Carb intake and exhaust

It isn't an air intake problem.
First, are you trying to run it in a barrel with the hood on? You can't do that.
Second, if you have it on a boat in the water and are getting smoke under the hood, the seal is missing off the top of the water pump housing. OR, if it is a long shaft the o-rings are missing off the round extension spacer. OR the round spacer is missing altogether.

OR one last possibility is the rubber do-nut seal around the midsection if in bad shape can allow exhaust to bubble up under the hood at idle. Not a problem at higher speeds because the exhaust is left in the wake.

OR one last, last, possibility is the rubber bellows hose on the exhaust relief (backside of motor, below the powerhead) could be missing or ripped.

Nothing goes on the carb intake except a chunk-stopper screen.

Re: Carb intake and exhaust

OR (ready for this?) one last, last, last possibility is the heat exchanger in the exhaust cover for the hot-air choke might be burned out.

Re: Carb intake and exhaust

Thanks, Y'all. Gives me lots to look for. Can't really find a 40 year-old go-by..
jer