Cant accelerate past 2800 rpm

[Sloppyjoe87]

I have a 1987 mercury 45 horsepower classic 50. It will not get on plane or rev higher than 2800 rpm when in gear. Carbs have been cleaned 4 times. New diaphragm pump. New primer bulb and hoses. New plugs, coils, switchbox, stator, and trigger. When I bought the boat 3 years ago every time it would sit a month or two it would be sluggish but once it got going it would run good. Even every outing after that unless it sat months again. Last fall as I was docking to load my boat I was hit by a tournament fisherman and knocked my lower unit into the bank. My prop was busted. Replaced prop with same prop and I've had this issue ever since. Could something be damaged in my lower unit or is it engine related? I checked compression too and all 4 cylinders were around 115 to 120. Starts easy and revs in nuetral in water. Any help would be greatly appreciated.

 

[roscoe]

Look for fuel system blockage.
From the fuel pickup in the tank, the hose, the primer bulb, fuel pump screen, all the way to the carbs.

 

[James R]

Most commonly issues like this are as a result of a cylinder not working. At idle try pulling the plug wires off one at a time and see if there is a change in the motor revs. The one that doesn't change it is the one to investigate further. Motors with a cylinder not working will usually rev just fine off load.

 

[hotrod53]

Be careful pulling wires off of a good coil. Not having anywhere to dissipate that electrical charge will cause a coil to eat itself. That charge will find its way to ground even if its through its own insulation. I had a guy leave a plug wire off after changing plugs and the coils arced out and ate itself.