Re: 1963 Johnson Sea Horse 75
IF that part really needs to be replaced it is quite a job. The powerhead has to come off, the lower unit has to come off, then the midsection has to come out of the outer "shell". Then the powerhead adapter plate has to be removed. Only Now, can you replace that rubber donut seal. It has to go over the top end of the exhaust housing. Yeah, I know, it looks like it would go over the bottom end, but it won't.
BUT before you get into all that, you had better make sure that is your real problem. Let me ask you one simple question: Does the smothering take place with the motor on a boat, on the lake, and at higher speeds? If it does, the donut is not the cause. Reason? Because the exhaust is buried in the wake far behind the boat and is not bubbling up around the shaft.
It could be the cause if the problem is only manifested with the motor on a boat, on the lake, and idleing in neutral at the dockside. Reason? The exhaust is bubling up around the shaft and being drawn up into the hood/carburetor.
A third possible scenario is are you running the motor in a tank of some sort? Forget it. Even a new motor wouldn't run in a tank with the hood on.
OK, bottom line: There is another, more common cause of the smothering problem. There is a foam rubber seal on top of the water pump housing. If that foam seal is shot or missing, it will smother out the carburetor, big time. Check that seal on the water pump before going any further!!!!