1975 20hp merc fuel issue???

MRJ82

Cadet
Joined
May 16, 2009
Messages
21
I have just purchased this motor from a gentleman that said he rebuilt the carb and that i should be good to go. It ran good in his barrel but when i got it out on the lake today at full throttle it seems to starve for gas. It starts bogging down and sputtering. i brought it back down to idle for a min or two and then opened it up again, it got to about 3/4 throttle and did the same thing. It kept doing this over and over. The last time i tried it, it got up to full speed and it started bogging and i squeezed the primer bulb for poops and giggles and it came right back to life running even better than it had, but kept having to squeeze the bulb to keep it at full throttle. So my question is did the gentleman mess something up in the carb, or is there a fuel pump on this motor that may be going bad? this is the first outboard i have owned so i am a new-bey at these. I have ordered a manual for this motor, but wondering is someone can help me out while the manual is in transit to my house.. Thanks for the help.
 

Case450

Seaman Apprentice
Joined
Jan 22, 2010
Messages
44
Re: 1975 20hp merc fuel issue???

i have an 86 merc 25 hp tiller that is giving me similiar problems. i changed my plugs, coils, wires, fuel filter, gas, gas tanks, new gas lines all around and pressure tested my cylinders (they held at 90 psi per cylinder). i finally gave up and took it to the mechanic..........i'll tell you what they figured out on mine so hopefully it will help you on your motor.
 

MRJ82

Cadet
Joined
May 16, 2009
Messages
21
Re: 1975 20hp merc fuel issue???

anybody have any ideas? I also installed a new gas tank, fuel line with primmer bulb and fittings, and it is still doing the same thing.
 
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