1989 merc 140 h.p. I/O stalls when slowly accelerating......

[jimbobma22]

My boat stalls/dies if I try to accelerate slowly from no wake to faster speed......however, if I punch it, it will take off....then I can bring it back down to a lower rpm........I just rebuilt the carb because of this and it is still happening.....any ideas? Thanks!!

 

[CharlieB]

Re: 1989 merc 140 h.p. I/O stalls when slowly accelerating......

When you cleaned and rebuilt the carb did you replace the accelerator pump CHECK VALVE?

A slightly leaky check valve will still seal enough to get somewhat of a pump shot with full throttle opening, BUT, small increases may not have enough volume to overcome the check valve leaking back into the float bowl.

Simple test, with the engine OFF. Remove the falsh suppressor and while looking directly into the carb watching the accel pump nozzle have a helper make small throttle increases or disconnect the throttle cable so you can open the throttle manually. Can you see a very small squirt from each nozzle? Try a larger throttle movement.

If no accel pump discharge on the small movements then R&R the carb again to clean that check valve ball and seat.

 

[Volphin]

Re: 1989 merc 140 h.p. I/O stalls when slowly accelerating......

Charlie's advice is right on the money. Sometimes it also helps to richen up the idle mixture 1 turn (out), and to slightly advance the timing. Be sure to reset your idle speed to factory spec though.

 

[jimbobma22]

Re: 1989 merc 140 h.p. I/O stalls when slowly accelerating......

Actually I did that when I put the carb on.....I moved the throttle on the carb before I hooked it up to the boat linkage and I got it to squirt fuel when I moved the linkage

 

[jimbobma22]

Re: 1989 merc 140 h.p. I/O stalls when slowly accelerating......

And yes I replaced both check balls ....acc. Pump...power valve ....all gaskets...and I made sure to put the aluminum ball in acc. Pump hole

 

[jimbobma22]

Re: 1989 merc 140 h.p. I/O stalls when slowly accelerating......

I will disconnect the linkage again and try slow pulls on the carb linkage and see if it stills squirts some fuel....if it is not, then do I tap lightly on the check ball to make sure it seats?