8hp Mercury dies when i give it some throttle

[frogseatflies]

I can put it in gear just fine, but giving it a little more throttle (maybe about 20%) eventually makes it die. It shakes a little and then dies as if it ran out of gas.

I've taken the cover off and did some testing in both neutral and in gear. I'll manually give it some gas by moving the lever inside (attached to the carburetor). I'm giving it about 20% gas before it dies. The rpm's go up as expected, but within 3 seconds it will shake and die. And when I say shake, I don't mean violently... just the normal running out of gas shake.

I gave it a carb clean maybe 3 weeks ago and have run it successfully a week ago on my boat on the water. No problems whatsoever.

Maybe the vibrations of transporting it in the back of my truck has bumped something loose inside?

 

[COYOTE54]

Re: 8hp Mercury dies when i give it some throttle

Frogseatflies,

Coyote54 here. I had the same problem with my 9.9 4 stroke. What a headache it was until I finally did something that all of the Mercury shops told me not to do.

I pulled my carb apart, yeah it was ugly with some old fuel gelling up in the bowl. Cleaned it all out with an overnight carb dip. Put in a carb kit and had the same damn problem. Finally posted on Iboats and somebody mentioned about the "top secret" air needle valve that's hidden behind a brass plug. Sure enough, when I drilled out the plug and unscrewed the needle valve to clean it, the dang needle valve had broken off inside of the carb body. So I very carefully drilled out the needle point with like a 1/32 drill bit. Put the new needle in there and the thing has run perfect ever since. But all of the Mercury shops told me not to mess with it even though the carb rebuild kit sends a new one in the packet of parts.

Check it out. I spent 2 years fighting the damn thing and was about ready to deep six it......

Runs like new.



Tim

 

[frogseatflies]

Re: 8hp Mercury dies when i give it some throttle

SOLVED: To everyone, I figured I'd report back. There was a bunch of junk upstream from the fuel filter. I've replaced the fuel filter twice now. I've even ripped open the fuel filter to see what was inside. Check it out: http://www.youtube.com/watch?v=nt7ggbkfCnc

How this crystallized junk was in there, I'll never really know. It could have been old gas?? Deteriorating fuel tank/hose/etc? I bought a new tank and hose just to be sure. I left the filter off, and just squirted gas through the really quickly to try to flush the hose hose leading up to the filter of all the junk. Junk came out. Dang. Of course this would block fuel flow to the engine. No problems now (other than low rpms). Working on that issue now.

 

[RadarRick]

Re: 8hp Mercury dies when i give it some throttle

I've seen that "crystallized" stuff. I would describe it like lumps of clear jelly. On mine, it was old gas, but I don't know how/why it forms. Thanks for posting the results.