1988 Mercury 2 stroke 15HP outboard fueling issue

[amf17]

I have cleaned and rebuilt carb but i'm still having a fueling issue. I have used multiple hoses and changed the gas (even tried engineered fuel) with the same result.

Engine has a tough time idling low and wanders (RPM up and down) at high idle. Bogs down when i give throttle and have to slowly open to rev up or it bogs and stalls. Carb Air mixture screw has to be almost all the way out (mercury recommends 1.5 turns out from fully seated, i'm at 5 turns out and tried every where in between). 1.5 turns and it won't even high idle.

Not sure where to go from here. any ideas or thoughts??

Andrew

 

[Dave1027]

Have you checked the fuel pump? You can do a quick test of the fuel pump by pumping the primer bulb while running. Does that help?

 

[jimmbo]

Perhaps the Carb has some Gum/Varnish/Dirt in the Idle and Off-Idle Circuits. How through was your carb cleaning?
How is the Spark, good enough to jump a 3/8 inch gap?
Are the Plugs, and Wires good?

 

[QBhoy]

Ultra sonic clean the carb.

 

[airshot]

Even after ultra sound you need to be sure all those teeny tiny passages are clear. Check for any vacuum leaks

 

[amf17]

The fuel pump on the side of the carb had all new gaskets etc installed. The carb itself is clean as a whistle, i did a very thorough job. Pumping the primer bulb doesn't really help no.

Thanks for replies everyone. I'll keep investigating and see if I can get somewhere.

 

[racerone]

How did this motor run last season for you?----Post compression test values.---Does spark jump a gap of 3/8" ?

 

[amf17]

Engine ran well for the most part. Bogged down a bit when going from idle to full throttle. Needed to slowly open throttle to get it to full speed sometimes. Now if I give full throttle from idle, it bogs and stalls immediately. I've also noticed quite a bit of fuel in the small poly tube connected to the bottom of the carb when running above idle speed(not sure if thats normal). Those tubes do not seem to be leaking or split at all.

Spark is good, but didn't do a compression test


Thanks

 

[airshot]

Not your fuel pump if squeezing the bulb didnt help, is the timing plate advancing when you throttle up? Otherwise it still sounds like a carb issue.

 

[amf17]

What about the reed valves? Possible culprit? I just disassembled the carb and reed assembly and everything looks good and clean. Possible that they are just worn out even though they look good?

 

[jimmbo]

Reeds rarely fail. If a reed was bad, you would have fuel all over the inside cowl, or if it has one, the Air Silencer.
I suspect the carb still has plugged passages. Also is the Possibility of the Carb and Spark Advance being of of whack. When you reinstalled the carb, did you did you do what is called a Link and Sync?