1975 1150 losing power at wot.

[pegithard]

my 1975 merc 1150 is losing prime at wot. i can pump the ball and it will pick right up, how can i fix this problem, i already have a ne ball and line on it, probably easiest fix is not to run at wot. also most of the post on here i read talk about these motors running at around 5000 to 5500 rpm. mine only turns about 4400 rpm,any reason for this. thanks david

 

[Plainsman]

Re: 1975 1150 losing power at wot.

I'd say rebuild the fuel pump pegithard.

 

[studlymandingo]

Re: 1975 1150 losing power at wot.

Not running at WOT isn't really a solution here. You could be running lean which can cause some issues with the internals of the motors.

Is the fuel vent unobstructed?

Most likely Plainsman is correct with the fuel pump; not a difficult rebuild. Do you have a manual?​

 

[roger3645]

Re: 1975 1150 losing power at wot.

I'd say if it picks back up when you squeez the primer bulb then it's time to rebuild the fuel pump. If you are only hitting 4400 rpms at WOT then you may be running a prop with to high of a pitch.

 

[pegithard]

Re: 1975 1150 losing power at wot.

the fuel vent is clear, how do i know if i am running to lean, i will get a fuel pump rebuild kit to see if that fixes the problem, i would like more info on it running to lean , i dont want to damage the motor, thanks for any help.

 

[pegithard]

Re: 1975 1150 losing power at wot.

oh yeah, my prop is a 21 pitch on a 17 ft. glastron.

 

[Chris1956]

Re: 1975 1150 losing power at wot.

Peg, You prop pitch is on the high side. Do you have PTT?

 

[Clams Canino]

Re: 1975 1150 losing power at wot.

my 1975 merc 1150 is losing prime at wot. i can pump the ball and it will pick right up, how can i fix this problem, i already have a ne ball and line on it, probably easiest fix is not to run at wot. also most of the post on here i read talk about these motors running at around 5000 to 5500 rpm. mine only turns about 4400 rpm,any reason for this. thanks david

Most likely a vacuum leak. Remember the pump SUCKS gas.

And yes.......... run at WOT all the time and you'll scrap it sooner than later. Put your car in 2nd and floor it for a couple hours - let me know.

-W