Please Help!!! 135 Optimax 2001, Idle great acceleration issue. Please Help

My grandfather gave me a boat. The motor has around 100 hrs on it. It was sitting for three years (Boat ran fine prior to it sitting). Mechanic changed spark plugs, water impeller, and lower unit oil, and did a small tune up before I got the boat this week. I drained the fuel and added fresh fuel then changed the fuel filter on the motor. I let it warm up at idle it sounded fine. The problem started around 1500 rpm the motor would drop rpm and sound like it was going to putter out, but would stay on. I ran it for around an hour and then the problem didn't occur till 2300 rpm. It seemed like it wasn't getting enough fuel. I am not for sure if this is the actual case. The ball on the fuel line was full so maybe some other can give me some suggestions??? I would greatly appreciate it!!!

Re: Please Help!!! 135 Optimax 2001, Idle great acceleration issue. Please Help

If this boat has been sitting for 3 years with untreated fuel, I would suspect damaged fuel pump(s). Do to the unique combustion process, the fuel has to be approx. 10psi above air pressure so fuel and air pressure is critical. After a compression test I would check those pressures. Their is a low pressure electric fuel pump that may have been compromised as well. After compression verified I would also rebuild the mechanical fuel pump too. Fuel should be 90 air 80psi.

Re: Please Help!!! 135 Optimax 2001, Idle great acceleration issue. Please Help

Definately compression check.Then spark check.It very well may be fuel related.Lors of things can develope porbs. sitting that long.Dont rule out electrical either.Bad stator can cause your symptoms also.Read up on testing it through search function on here.Could be other electrical as well.Just need to start testing stuff to CHEAPLY find the cause.And +1 on rebuilding fuel pumps.Replace all gas lines and bulb also.Sitting kills these things and if not attended to,will kill your motor.good luck.

Re: Please Help!!! 135 Optimax 2001, Idle great acceleration issue. Please Help

How much do you think it would cost to rebuild the fuel pumps?

Re: Please Help!!! 135 Optimax 2001, Idle great acceleration issue. Please Help

Again,i dont know your motor but It shouldnt cost over $100 probably a good bit less.Provided you do it and not someone charging $100/hr labor.Its easy to do.

Re: Please Help!!! 135 Optimax 2001, Idle great acceleration issue. Please Help

If it is the fuel pump, high pressure about 500-600 bucks, the low pressure maybe 100-150. But this is something your mechanic should have tested especially after sitting this long. If it turns out to be the fuel pumps, you may be able to salvage them by putting them in an ultrasonic cleaner, but they may not free up. Whenever you do get everything back together, you have learned the most important lesson about the internal combustion engine...letting it sit untreated is the worst thing you can do.