74' or 75' merc bogging down at full throttle.

[arls14skiff]

I have a 1974 or 75' mercury 20 hp outboard. I actually found it in the trash. It has almost no hours on the motor. I had the water pump changed and the coils changed along with new fluids. Now, when I'm at full throttle it holds for about 30 seconds, and then it starts to bog down and then shuts off. Does anyone know what to look for? I did put a new fuel line and tank on. I really appreciate the help guys.

 

[AMD Rules]

Re: 74' or 75' merc bogging down at full throttle.

I'll ask my usual question....

Is the vent open on the fuel tank?

If not that, it sounds like a weak fuel pump or a restriction in the system.

Carbs been rebuilt? Perhaps they have some 'trash' in them?

 

[arls14skiff]

Re: 74' or 75' merc bogging down at full throttle.

Yea, I always keep the vent open. I had the carb rebuilt already... I have a feeling it could be the fuel pump, but i have no idea on how to fix it. Thanks buddy.

 

[AMD Rules]

Re: 74' or 75' merc bogging down at full throttle.

Good news is that the fuel pumps are quite easy to rebuild.

 

[DJ_Allatoona]

Re: 74' or 75' merc bogging down at full throttle.

Yea, I always keep the vent open. I had the carb rebuilt already... I have a feeling it could be the fuel pump, but i have no idea on how to fix it. Thanks buddy.

Fuel pump rebuild is one of the easiest things to do with outboards. It's just a new rubber diaphragm and gaskets. $8 or $9 max. Open pump housing, remove old, replace with new. Even if that isn't the root of your problem, new pump rubber always improves your performance a bit (better idles, etc.)