Re: Mid 50’s Johnson 25HP runs like crap. Advice needed

[Don]

OK, watched the video but wondering why you are not attempting to adjust the low speed needle? I noticed that killing the top cylinder does not seem to affect it much…Is the tank pressurizing? Perhaps one of the rubber tank pressure valves in the manifold is messed up. Does it look like the intake manifold has been messed with?
I don’t want to lead you down a bad path though. You might consider putting that engine on a boat and trying it first, before getting in too deep…