[brentusm]

I have a 2002 Yamaha 150 OX66 2 stroke. I had a problem last year where the primer bulb would collapse causing the engine to run lean and eventually stall. I bypassed the fuel water separator and the engine ran like a champ. When back on shore, i went out and replaced the entire harness and filter for the fuel water separator with a Racor product. I also replaced the primer bulb but with a generic from wally world. Engine ran great the rest of the summer.

I took it in for the spring tune up this year. I was told by the mechanic that the fuel water separator was replaced and i have verified that. I ran it this weekend and after about 45 minutes running at 4500 rpms, the problem has returned. I could turn the valve on the racor and the buld would regain shape. I would prime it up and i could only run for about 10-15 at higher rpms. At lower rpms, i could run as long as i wanted. The boat sat up for about 4 months this winter and i failed to put in the StaBil. I know that was a mistake but i had my first child in october and she didnt leave me much time to do anything else. I did crank the engine periodically while is was dry docked.

I am going to replace the primer bulb with a Yamaha bulb. I have two questions. Should the primer bulp be in line with the engine or should it be before the fuel water separator? And, am I missing something else that i should try?

Im a computer technician not an outboard engine mechanic so i need a little spoon feeding on the tips. Thanks for your help in advance!

[rodbolt]

about the most ignorant thing you can do is to bypass a clogged filter, means any trash/water now goes directlty into the engine.
I prefer the water seperator to be between the filter and the engine but its not critical as all it is is a primer, once the VST is full you can remove the primer and run forever.
if it collapses during running it means there is a restriction between the primer and the liquid level in the tank and nothing else.
but now its time to service the filter in the VST and the one on the engine, change the element in ytour racor as well.
keep running it lean and you will post about low compression in #1 cylinder

[jl_photo]

I think that you might have a clogged fuel pick-up or a clogged air vent in the tank.

the air vent is easy to check, just open the gas cap while you are seeing the primer bulb collapse, if you hear air sucking into the tank when you take the cap off then that is your problem. bugs like to build nest in vent holes.

[snowmon]

check the anti-siphon valve where the fuel line connects to the pick-up to the tank. will cause a collapsed primer bulb. have you changed to e10 fuel? that was what screwed up my system. valve was stuck closed by small grains of crap.