Re: 1959 10 Hp Johnson Seahorse Boat Motor
If the check valves are shot which I've never encountered before (keep in mind F-R was working on these before I was born so if he says it, that's how it is), then you'll have to remove the carb, then remove the intake manifold and you'll see them. They'll be a pair of little black things that are totally obvious since other than the reed valves, they're the only thing in there. After you get the intake off they're totally easy to replace. I would take the air hose off the tank and see if air was being pushed out by the motor before I'd take that intake off to check the check valves. If you pry on that intake too hard because you missed taking out a screw and can't figure out why it won't come off, then game over unless you can get a new intake. There's a screw or two on the intake manifold that are not obvious and easily missed.
Myself, I'd suspect you have a blockage somewhere such as the fuel filter, fuel line to the carb, or fuel connector itself. Why don't you take the fuel line off the carb and pump the primer, then see how much fuel comes out. If it gushes out with no resistance, then take the carb off and take the bowl out and pump the primer and see how much is coming into the carb to see if your filter may be stopped up. Or you could even take the filter element out momentarily to see if that fixes the problem. Lastly, if all that checks out o.k., I'd suspect your float is misadjusted and you're having to force fuel past the needle valve with the primer to get it to go into the carb and fill the bowl up. I'd just make sure I covered all my bases on fuel restriction or float adjustment before going to the check valves.
Just some ideas you might try,
JBJ
