99 9.9hp mercury

ggentry

Recruit
Joined
Jul 8, 2009
Messages
3
so my buddy has this 9.9hp and we used it just great for the first 3 weeks i was home from afghanistan. one night it died at full throttle and since then we can't get it to perform at full throttle actually full throttle will kill it. It starts fine idles great, but full throttle is a killer it doesnt even run rough just when you turn the throttle all the way open it bogs and dies. We have changed the spark plugs and made sure the fuel line coming from the tank is free of any debris. Every now and then it wants to run a little faster but still dies with full throttle but this requires the choke to be pushed in and out depending on what it wants just listening to it. Any thoughts?
 

green4themoney

Petty Officer 1st Class
Joined
Jul 21, 2004
Messages
318
Re: 99 9.9hp mercury

first off, is it pumping correctly? make sure its not overheating for starters, if thats not the case then it simply sounds like its getting too much gas... maybe i wonder if the main jet was changed or anything?
 

green4themoney

Petty Officer 1st Class
Joined
Jul 21, 2004
Messages
318
Re: 99 9.9hp mercury

ORRRRRRR your fuel pump might need a rebuild, may not be giving adequite supply to the carb
 

ggentry

Recruit
Joined
Jul 8, 2009
Messages
3
Re: 99 9.9hp mercury

i was thinking maybe fuel pump as well, i rememberd he said that the bulb coming from the tank will get soft instead of staying firm while its running. everything in the motor is original he hasnt changed anything and we didnt change anything before it started this problem it just started on its on.
 
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