Can’t get full rpm from port motor

Civility

Member
Oct 7, 2020
81
Center Moriches, New York
Boat Info
2000 Sea Ray Sundancer 310
Engines
357 Horizon w/ v-drives. Repowered in 2015
Good morning. Perhaps someone can help me. I have a 2000 31 Sundancer. re-powered in 2015 with MerCruiser 357 Horizon. There currently is 321 hours on the engines. Port motor will not go above 3200 RPM. Took the spark arrestor off and gave full throttle and the butterfly opens completely. After that, I don’t know what else to do. thoughts
 
I don't think you have a fuel selector valve, right? Try swapping fuel lines... meaning, plumb it so the port engine runs off the stbd tank. But before you do that, try running with the port fuel fill cap off.
 
I don't think you have a fuel selector valve, right? Try swapping fuel lines... meaning, plumb it so the port engine runs off the stbd tank. But before you do that, try running with the port fuel fill cap off.
I am not a mechanic by any stretch of the imagination. I’m a Carpenter. That being said, my fuel filters were replaced at winterization end of season last year. Think I should try replacing filters also?
 
When was the last time it ran right? What has been changed since then?
 
It hasn’t run right all season. Last time it ran right was last season before winterization and layup. Only thing that’s changed was fuel filter!?
Ok so check everything that was done during winterization. First, make sure the fuel filter is seated properly — may have left the old seal on creating an air leak. Check all the plug wires - make sure they are seated. Etc. Easy stuff first.
 
Something could have got knocked loose or knocked off during the winterization process give everything a really good look over
 
The "re-plumbing" is very basic - if you're a carpenter it will make complete sense once you look at it. It's really just changing some hoses around. It's just black hoses instead of sticks :)

But... grab a spaghetti jar and remove your fuel filter (it just screws off). Pour it into the spaghetti jar and let it sit for an hour or two and observe (and/or post a pic). This will tell us the quality of the fuel.
 
The "re-plumbing" is very basic - if you're a carpenter it will make complete sense once you look at it. It's really just changing some hoses around. It's just black hoses instead of sticks :)

But... grab a spaghetti jar and remove your fuel filter (it just screws off). Pour it into the spaghetti jar and let it sit for an hour or two and observe (and/or post a pic). This will tell us the quality of the fuel.
Thanks for the thoughts and insight. I’ll be back to the boat next weekend and will try these things. I’ll keep you posted and let you know how it works out.
 
Ok so check everything that was done during winterization. First, make sure the fuel filter is seated properly — may have left the old seal on creating an air leak. Check all the plug wires - make sure they are seated. Etc. Easy stuff first.
I think this happens more often than is admitted to.
I know . . . I've seen me do it. :rolleyes:
 
I think this happens more often than is admitted to.
I know . . . I've seen me do it. :rolleyes:
Yeah. I did it once on an old style canister filter. Didn't get the gasket seated properly. Engine started up fine and died a few min. later. I crapped my pants and then figured it out.
 
Are you up to date with all of the mechanical maintenance?
 
Are you up to date with all of the mechanical maintenance?
Meaning??? I have the engines winterized by a licensed boat mechanic. filters are changed along with fluids... He has been doing this for me for 3 years. Other than winterization... no other maintenance has been required.
 
ers are changed along with fluids
Meaning??? I have the engines winterized by a licensed boat mechanic. filters are changed along with fluids... He has been doing this for me for 3 years. Other than winterization... no other maintenance has been required.
Plugs, Rotor, Wires, Cap?
 
Meaning??? I have the engines winterized by a licensed boat mechanic. filters are changed along with fluids... He has been doing this for me for 3 years. Other than winterization... no other maintenance has been required.
Meaning….following the service intervals in the owner manual for the mechanical systems usually means years of trouble free operation. When was the boat last tuned up with new plugs and spark plug wires?
 
Could be as simple as needing a tuneup. Have you changed your spark plugs since the rebuild?
 

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