2003 Mercury 40HP 2 Stroke - can't get to WOT

[mattfish11]

Hey group! I've searched for similar topics on here, but can't find anything I can go off of.

So - I have a 2003 Mercury 40HP 2 stroke. Fires up and idles fine - aside from a loud scream from something. No idea what that is - maybe the starter? not sure.

Anyway - I idle great, move along great until I want to open it up and get to WOT rpms... I get up on plane good but can only max out at 4000 rpms. My rpms used to get up to 5200-5300. Any ideas on what's going on here? I have the same prop as before, haven't changed anything...

Any quick ideas i can check on before hauling to a boat mechanic?

Thanks!

Matty

 

[mattfish11]

Re: 2003 Mercury 40HP 2 Stroke - can't get to WOT

I'm going to go ahead and replace all the fuel lines from the remote gas tank to the motor as well as the fuel filter. Hopefully that will do it.

I don't know what else it could be...

 

[captkevin]

Re: 2003 Mercury 40HP 2 Stroke - can't get to WOT

Lots of things could cause problems.
Do you keep it in the water - marine growth would cause the problem.
How is the prop? Any damage could slow you down.

 

[mattfish11]

Re: 2003 Mercury 40HP 2 Stroke - can't get to WOT

no - its not kept in the water...

The prop is in pretty good shape - i tiny ding here and there. But I have a spare prop that I threw on it just to ensure that's not the problem... didn't help at all.

I think there is some restriction with the fuel flow... booo... i'm going to do some work on it this week, replace the fuel lines and filter and see if that changes anything...

 

[mattfish11]

Re: 2003 Mercury 40HP 2 Stroke - can't get to WOT

I fear something bad... just replaced all fuel lines and fuel filter. NOTHING changed - still getting it up to 4000 rpms and can't get it any higher - hammer down...

 

[Vernkim]

Re: 2003 Mercury 40HP 2 Stroke - can't get to WOT

I fear something bad... just replaced all fuel lines and fuel filter. NOTHING changed - still getting it up to 4000 rpms and can't get it any higher - hammer down...

What was the final outcome?

 

[bernptl49]

Re: 2003 Mercury 40HP 2 Stroke - can't get to WOT

I fear something bad... just replaced all fuel lines and fuel filter. NOTHING changed - still getting it up to 4000 rpms and can't get it any higher - hammer down...

I did the same thing. I even did the coils as mine will stay ok at WOT until warm and then will shut down. None of the fuel system fixes work. I think the next step is to have a marine mechanic check it out. Possibly the reed valves?

 

[nipperdog]

I'm going to go back to the first post. Did you figure out the loud screaming issue? Did this screaming happen out of the blue, or had you just filled the fuel tank? Was the motor in storage for a long time? Have you taken the cowl off to see if the starter gear is hanging up and causing the noise? An easy test that will sometimes show a bad reed valve is to run the motor in neutral at a slightly high RPM and carefully put your hand in front of the carb intake a couple inches away. If you feel air coming out, you have a suspect reed valve. If working correctly, the reed should only allow air to go into the carb, not out. Hopefully this screaming is not your motor trying to seize. A compression test would be in order too.

 

[GA_Boater]

This thread is over 7 years old. By this time the OP fixed it, junked it or sold it.

Closed.