How to test fuel pump - also idiot question about kits.

[Aces_Up08093]

Well I've been having a problem with my 76 johnson 55hp where it runs good at idle / mid-throttle but dies at high throttle. From the diagnostics I've been able to do combined with EVERYONE I've asked saying it sounds like it's "starving for fuel", I'm leaning more and more towards it being the fuel pump.

The pump is $80, so before I go buy it I'm wondering if there's a way to test the one that's in it. The guy I baught it off said he replaced the fuel pump, but I don't know if he was just blowing smoke up my ass. Also, there's a fuel pump kit for $12, is that a rebuild kit?

Thanks

 

[F_R]

Pump the primer bulb when it tries to die out. If that keeps it running, it indicates a fuel pump problem. OR a leak anywhere between the fuel pump and the level of fuel in the tank. OR a plugged up fuel filter.

 

[kbait]

You can also pull the pump, shake out the fuel, and suck/blow through the ports. Air should only pass 'in' through input port, and 'out' through output. That said, if you pump the bulb and it doesn't help, and it's actually starving for fuel, it's not the pump, as per F_R above. If it's flooding one cylinder, your pump could have a small hole in the diaphram, letting fuel into the cylinder it draws from. You could check/compare that plug w/another in that case to see if it's wet w/fuel.

I've seen the float level cause your exact issue on an '80's vintage 25hp. With float set level w/carb body when inverted (as per manual), it'd starve for fuel over 3/4 throttle. I set the float 'aimed down' a bit from spec, and it ran fine with slightly more fuel in bowl. Haven't seen that since, but may be worth a try..

Good luck!

 

[Aces_Up08093]

You can also pull the pump, shake out the fuel, and suck/blow through the ports. Air should only pass 'in' through input port, and 'out' through output. That said, if you pump the bulb and it doesn't help, and it's actually starving for fuel, it's not the pump, as per F_R above. If it's flooding one cylinder, your pump could have a small hole in the diaphram, letting fuel into the cylinder it draws from. You could check/compare that plug w/another in that case to see if it's wet w/fuel.

I've seen the float level cause your exact issue on an '80's vintage 25hp. With float set level w/carb body when inverted (as per manual), it'd starve for fuel over 3/4 throttle. I set the float 'aimed down' a bit from spec, and it ran fine with slightly more fuel in bowl. Haven't seen that since, but may be worth a try..

Good luck!

*sigh* I really should rebuild the carbs... The guy I got it from said *that* was done also, but I don't know how truthful he was being. I just wish I could find a definitive guide TO rebuilding the carbs on this thing. Do you think if I purchased the rebuild kits listed on Iboats it would come with instructions on setting the float, needles, etc?

 

[bonz_d]

With age of an engine with unknown history I would rebuild the carbs and replace all the fuel lines on it. All the Sierra rebuild kits that I've bought had a quick guild with pictures on setting floats.