Re: 50hp force us marine occasionally idles rough
Welcome to iboats.
Kind of surprised this went unanswered for a whole day.
Sorry, must have missed it.
You are experiencing a classic flooded engine.
While you are sitting and fishing, the fuel is leaking into the powerhead and flooding it.
By going full throttle and cranking, you are clearing out the excess fuel.
There is a very good chance that your fuel pump is the culprit. Don't worry, rebuilding it is pretty easy, and cheap.
What is likely happening:
You run the engine, then shut it off.
THere is fuel in the pump, and it starts to leak through the diaphragm in the fuel pump.
Why?
Because the diaphragm is old, being dissolved by our modern gas that contains ethanol, and possibly has a small whole, or a tear in it.
THe fuel systems on these older motors were not ethanol resistant, and they have been failing a lot.
THe fuel seeps through, and runs into the powerhead. The pump uses pressure pulses from the powerhead to move the pump, so yes, it is open to the powerhead.
So now you have excess fuel puddled up in the crankcase, and this will go directly into the cylinder and flood it out.
So, you order up a fuel pump rebuild kit from Mercury, it should come with instructions, and cost about $15.
If you have a repair manual, you can use that for instructions, and buy your kit right here from iboats, and save a buck or two.
Takes about 25 minutes to do it.
