2003 40 hp merc lost top end rpms

[lpwebb]

I have a 40 hp mercury that i have used for 3 years now but it has devoloped a problem. I have lost all of my top end power. I went fishing yesterday and it ran fine . then all of a sudden it slowed down and would not rev over 3000 rpm. My primer bulb was hard and pushing in the choke would do nothing. It starts and idles fine however it will not open up. please help me andy advice is appreciated.

 

[Nos4r2]

Re: 2003 40 hp merc lost top end rpms

Have a read of this post and see if it helps. I had what sounds like exactly the same problem a few days back on my 50hp merc.<br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=29;t=017338

 

[lpwebb]

Re: 2003 40 hp merc lost top end rpms

how did you resolve this problem?

 

[dajohnson53]

Re: 2003 40 hp merc lost top end rpms

Have you checked the spark plugs?

 

[Laotzu]

Re: 2003 40 hp merc lost top end rpms

I recently had an identical problem with my 50. It was flakes of varnish in the #1 carb. Ok at idle but when power applied, it sucked one of the flakes into the jet, so it was essentially running on 2 cylinders thus max rpm was 2800. Took off the carbs and cleaned good with cleaner and blew out with compressed air. Runs great now.<br /><br />Jerry

 

[Nos4r2]

Re: 2003 40 hp merc lost top end rpms

That's exactly what my problem appeared to be. My lower carb was full of brown gooey flakes.<br />Starts and runs noticeably better on muffs now-though it sounded ok before.Can't water test for another week or so though.

 

[Laotzu]

Re: 2003 40 hp merc lost top end rpms

ipwebb, looks like carb gunk might be your problem if Nos and I had the same thing. Worth a try and not difficult to do.<br /><br />Jerry

 

[cistn]

Re: 2003 40 hp merc lost top end rpms

don't know if you read any of my post here, but, my engine was having issues,low rpm,stalling when i throttle up etc. took it back to the dealer and they changed the STATOR..seems to be an issue with merc, engines,don't know why,never got an explanation, got the boat back yesterday, seems to run with much more HP and reliability.seems the STATORS on merc, crap out if you let them sit for a season or so.(my guess not fact)my i can get to 26 MPHon a 30 hp merc, on a GPS..and have more throttle to go,,,,,,,,,,,chuck

 

[lpwebb]

Re: 2003 40 hp merc lost top end rpms

stator is what scares me

 

[lpwebb]

Re: 2003 40 hp merc lost top end rpms

i found a loose plug wire at the coilpack playing with it got me back most of my power. im hoping replaceing it will give me the rest of it back. if it does not i will look at the carbs.