Late 80s 9.9 - Stalls in the midrange?

[hoeser]

I've got a very-late 80's Mercury 9.9 that is exhibiting some odd behavior but only under mid-throttle conditions. I can start the engine wonderfully 1st pull every time, cold, hot, doesn't matter. It will troll around at idle all day with no issues and when you get up on it it runs excellent wide open. It will push my 10' Quicksilver inflatable up to 23mph. The issue I have is in the low speed/mid range, when you crack the throttle much past idle (say 20% power) it bogs like its starved for fuel and then stalls It will restart in neutral first pull every time. If you advance the throttle past this "cut out" point, (to say 60% power) it will spring to life.

Any ideas?

Thanks!

 

[dennyb123]

Re: Late 80s 9.9 - Stalls in the midrange?

It sounds like the fuel pump may not be functioning properly. When it needs that quick burst of fuel its just not getting it to the carb quick enough. You may have to to a carb overhaul.

 

[hoeser]

Re: Late 80s 9.9 - Stalls in the midrange?

Pumping the fuel bulb yields no results so I'm pretty sure its not the fuel pump, also, quickly applying power is what WORKS.. oddly enough... it only cuts out when you gradually move past 20%.. between 20 and 55% power it just dies off.. if you quickly advance from idle to 60% or greater power, it runs fine. It just doesn't like running in that midrange area.

 

[rtpassini]

Re: Late 80s 9.9 - Stalls in the midrange?

sounds like a needle height/ clogged jet problem.

 

[hoeser]

Re: Late 80s 9.9 - Stalls in the midrange?

Seems like the consensus is Carb Rebuild?

 

[rtpassini]

Re: Late 80s 9.9 - Stalls in the midrange?

i wouldnt say rebuild. unless you have the money. start cheap. make sure they arent gummed up and go from there.