94 Merc 115 - Loss of Power low RPMs

Rebuilt carbs, rebuilt fuel pump and changed out fuel filter. Took boat out set the idle screws as instructed by help from a previous thread I posted (thanks CharlieB). Got a great idle setting IN GEAR and IN the water. Had to run a few hole shots to get the overall idle setting right...but once set the boat jumped out of the hole and cruised faster than ever has before. Things were going so well I decided to do a little fishing.

Fired up the engine to make run back to ramp and this is when it went south. Engine bogged down and died for first hole shot...and when i got it to run there was no top end speed. Could only get 4k RPMs instead of just short of 6k RPMs that i normally get at full speed. Boat barely got up on plane....and as it was struggling to get full power the engine was surging and kind of jumping but never locked in on top end RPMs.

Only thing in the fuel system i have yet to change out is the accelerator pump for my 2 + 2 system....can those go bad or get clogged? Am I heading in the right direction or is there something else i didn't think of?

Thanks

Re: 94 Merc 115 - Loss of Power low RPMs

Accel pump nozzles can get clogged and kill the hole shot, but the accel pump only moves fuel AS the throttle is being opened. Once the motor is up to speed there is no further fuel flow thru the accel pump and injector nozzles.

Surging is often caused by;

weak fuel pump

fouling and clearing spark plugs

Inspect the plugs to be sure all are about the same good condition.

Disconnect the fuel hose to the carbs, crank the motor and watch for a strong pulse fuel flow.

Reinstall using a temporary clear hose, start and run the motor and watch for any air bubbles passing thru the hose indicating air sucking into the system anywhere before the fuel pump.

If you have the boat on the water, have a helper keep squeezing the primer bulb, if this improves RPM then immediately rebuild the fuel pump and double check all hoses.

Running lean, with a restricted fuel supply will fry the motor. You want to get this tested and figured out quickly, before you hurt your motor.

Re: 94 Merc 115 - Loss of Power low RPMs

CharlieB - Thinking about the squeeze bubble trick. Could that possibly be why the engine ran great at first because i pumped the bubble a bunch and filled up the carbs manually. Then they got low after running for a bit and the fuel pump or fuel lines were not doing their job? I found a local place that sells the clear fuel line. I will be picking some up today.

Thanks again