Primer Bulb Wouldn't Firm Up & Intermittent Sneezing At Low Power

[kestrel452]

In regards to my 1999 Mercury 15HP 2-Stroke....

I changed the fuel line to a genuine Quicksilver quick connect style line, and replaced the EPA cap on my Attwood tank with a Moeller venting cap (which fit just fine). It was the pre-assembled 8' line with the standard 1/4" thread on one end, and quick connect engine fitting on the other. Had a full tank, and verified that the engine side connector was snapped in place, but the primer bulb just wasn't firming up. Even the crappy Attwood line I had before would firm up pretty quickly after a few squeezes, but this one just wasn't having it. The engine managed to start when i hit the electric starter, though. After leaving the dock and meandering through the no-wake zone to head out, the engine was "sneezing", and continued to do so at times when we were running at less than 1/3 to 1/2 throttle. Could this be caused by a bad bulb????

I also noticed a slight squeal coming from the engine when bringing it down from full throttle that'd last a couple seconds.

The engine should be okay mechanically, I've had it inspected by multiple reputable shops. The only thing that's been done to it recently is the installation of a Permatim hydrofoil (since the inflatable I have it on wasn't planing), and me installing a lower pitch (7 pitch) prop from the stock 9 to bring the RPM's up a little. I sprayed everything with Corrosion X oil, including the thrust washer, spines, prop, shaft spines, and nuts before putting everything on and cranking the prop nut down.

Any thoughts???

 

[kestrel452]

UPDATE: Tried squeezing the primer bulb just now with the line connected to the tank but not the engine and it firmed up nicely.... Strange....

 

[gm280]

Well if the primer bulb will not firm up when connected to the engine, you have either a fuel pump issue or carb issue. And either can cause the sneezing and problems throttling as well. So look into those things to see what is the problem. The fuel pump could have a hole in it or the carb needle and seat could be not sealing off the inflow of fuel... May be time to rebuild them both! JMHO!

 

[kestrel452]

Well if the primer bulb will not firm up when connected to the engine, you have either a fuel pump issue or carb issue. And either can cause the sneezing and problems throttling as well. So look into those things to see what is the problem. The fuel pump could have a hole in it or the carb needle and seat could be not sealing off the inflow of fuel... May be time to rebuild them both! JMHO!

It's nothing mechanical with the motor, it was just rebuilt and then inspected by multiple shops. I can't do anything except rule a mechanical failure out.

The only thing I am thinking is that it's "normal" for brand new primer bulbs to have trouble priming fuel when they're first used and have never seen fuel go through the line before. Is this true or am I simply making things up?

The sneezing could possibly be from too lean an idle mixture, I don't know, what do you think?

What has me stumped is the squeal when coming down from WOT. Only thing I can think of is that Corrosion X isn't a good enough lubricant to have used when installing the new prop.