Help, Im lost with my 3.0 Merc

[jac09g8gt]

I have been fighting a stumble problem, so I changed out the fuel filter. I took the boat out Saturday and it started surging really bad at low rpms. It would surge about 500RPMs when in the 2000-3500RPM range. When I got the boat out and ran it wide open, it ran great. When I went back to low RPMs it would surge back and forth and sometimes die out. I am about to give up and bring it to a dealer at this point. Any suggestions?

Details:

2000 3.0L Mercruiser
Surging throttle at lower RPMs, runs fine at high RPM. Idles fine and runs ok on muffs.

 

[zbnutcase]

Re: Help, Im lost with my 3.0 Merc

Time for a carb rebuild, sounds like dirt or varnish in the transition circut

 

[jac09g8gt]

Re: Help, Im lost with my 3.0 Merc

Time for a carb rebuild, sounds like dirt or varnish in the transition circut

The carb was rebuilt last year, but I guess its possible because I lost hope in that mechanic. I am moving on to a mercruiser certified shop this time. This is off topic, but is there anything to do to the motor to get more power out of it (exhaust, or different carb)? Also, since the carb was rebuilt last year, should I just get a new one?

 

[TiredoleBoy]

Re: Help, Im lost with my 3.0 Merc

You may have a piece of dirt stuck in the idle circuit causing gas to spit into the bowl during idle. WOT would accept this additional gas so it would run fine then. I would take it apart and see what the bowl looks like. before condemning the carb.

 

[jac09g8gt]

Re: Help, Im lost with my 3.0 Merc

Thank you for the replies. All of your help is appreciated.

 

[BIGALF]

Re: Help, Im lost with my 3.0 Merc

start from the beginning. Is there a clogged screen inside the tank where the tube pulls fuel from the tank? This is a cheap check. I drove the service guys crasy until I told them to check the screen and we found that it was clogged and when the boat first started it ran but over time it got clogged from all the slushing of the dirt in the tank.

 

[jac09g8gt]

Re: Help, Im lost with my 3.0 Merc

I gave up and brought it to the dealer

 

[jac09g8gt]

Re: Help, Im lost with my 3.0 Merc

I have had the boat run on muffs on my inclined driveway and no clogging. I did leave it at the mercruiser shop today and I will update the thread when I get the solution for the boat so people searching can see the cure of my problem. Thanks for the help.

 

[jac09g8gt]

Re: Help, Im lost with my 3.0 Merc

I got my boat back today and the carb had a little trashin it. The carb was rebuilt with the wrong needle in it also. Good thing I found a new mechanic. Everything checked out fine otherwise.

 

[myoldboat2]

Re: Help, Im lost with my 3.0 Merc

i'd still check for any water in the tank.

 

[jac09g8gt]

Re: Help, Im lost with my 3.0 Merc

I did put a fuel/water serperater kit on the boat also. It never had one and I started putting the mercruiser fuel stabilizer in each tank. They did have to replace cylinder #3 spark plug because it was flooding in that cylinder. All cylinders came out fine with the compression test. They ran the boat on the river and said it ran great. I have not had a chance to get it out on the water yet to see for myself.