air intake issu?

I've got a 50HP 87 Force 2 stroke. I've rebuilt the carb (twice) last year, replaced temp sensors, fuel pump, water pump and plugs. I had a lot of difficulty with idle last year but my second carb rebuild and an adjustment to throttle on idle and it's much better. However, I had an issue with top end speed. This year I wasn't able to get the boat on plane. When it get's to the top end it just seems to bog down - you can feel and hear it.

So I took the prop off and put the rear in a trashcan full of water to I could really test the top throttle. First start, same issue. I took the cover off and tried again - this time it ran great. Hmm? put the cover back on - top speed - bogged down. This time i left it run at top throttle while i took the cover off and as I was taking the cover off it got better instantly. and as i let it run it started to hit a super hand band when a gust of wind blew away the exhaust that was accumulating around it.

So I clearly have an issue with the air intake. Point of note, the foam on the inside of the case was all rotten and gross so I ripped it out last year. Was that foam somehow filtering the air? there really is no air vents on the cover at all. Should I cut some slots in the cover? I'm most concerned about water getting in there while it's on the water. Is this something I should do? Is there another way to get air in there without major modification to the case?

Thanks

Re: air intake issu?

The problem is an exhaust leak, leaking into the cowl, choking off the oxygen supply.


Probably find your exhaust leak at the adaptor plate, or below it in the leg.

I don't know what a super hand band is, but guessing it will be the least of your problems if you continue to run it at full throttle without a load.

Re: air intake issu?

I meant super high band. like on a 2 stroke dirt bike when you hit the power band and it really takes off. wouldn't the 2 stroke outboard work similarly?

As for the exhaust leak, i think you might be right. upon further inspection when i first get it going at full throttle it smokes like crazy. it seems to settle into a nice even "high band" after a few minutes and the smoke clears. the smoke may also clear because i've thrown out more water in my can that I can add with the hose, so the water level get's low. not totally sure if they are in correlation.

How can I test for an exhaust leak? Also, what is the danger in running it without the prop? how can i test the high end then?

thanks for your insight.

Re: air intake issu?

You don't have to test for an exhaust leak, you already have seen what one does. It causes your engine to run bad with the cowl on. I don't know if a f50 horse has a rubber coupling at the rear of the leg but, if it does, replace it and you may fix your problem.

These hoses get brittle over time and leak.

John

Re: air intake issu?

You are gonna need a repair manual, a Clymer or a factory manual.
Likely gonna have to remove the powerhead to replace the gasket below it.