RPMs limited to 4200

[r_moss]

My 2004 300 Sundancer is acting up. She used to be well behaved but recently started acting up.

She is holding back. When I give the twin 5.0s full throttle to come up on plane she is being stubborn, and won't run over 4,200 RPMs. It seems like the motors are being held back on purpose. Possibly the ECMs?

I would love to get some feedback from one of our resident experts on what can cause this problem. BTW, I did have her bottom power washed and the problem is still there.

The motors only have 420 hours and she never gets ethanal.

Thanks ahead of time.

Rick Moss

 

[The Bill Collector]

Fuel filters....? I know to easy, but what the hay...

 

[edsmax]

Raise your drives and look at the props. I bet you have a marine growth problem either on your props or bottom (or both). WHoops, just re-read your post and you already had the bottom power washed. My next guess would be a fuel issue.

 

[lope4946]

Had a similar problem on one of my 4.3's. Turned out that the fuel backflow valve on top of the fuel tank was clogged and was starving the engine for fuel. I can't remember if the mechanic replaced or just cleaned the valve. Problem solved.

 

[CliffA]

Had a similar problem on one of my 4.3's. Turned out that the fuel backflow valve on top of the fuel tank was clogged and was starving the engine for fuel. I can't remember if the mechanic replaced or just cleaned the valve. Problem solved.

i believe you mean the 'anti-siphon valve'...it is a safety devise designed to prevent fuel from being siphoned out of the fuel tank and dumped into the bilge if the fuel line ruptures or is somehow disconnected from the fuel pump....lots of discussion on the forum about this valve the past few weeks.....you are right that it can starve the engine from fuel if it is partially clogged or the check ball becomes stuck.....

cliff

 

[lope4946]

Wasn't sure about the name of the valve but it was a pretty easy fix once we figured out the problem.

 

[CliffA]

Wasn't sure about the name of the valve but it was a pretty easy fix once we figured out the problem.

yea, i didn't even know it existed until a few weeks ago and was having issues of fuel starvation....

i see you are from Aiken...my daughter-in-law is from Aiken....do you happen to know a police detective named Larry Cleveland?...he is her father...

cliff

 

[lope4946]

Cliff, sent you a PM.

 

[r_moss]

Have a local mercruiser mechanic coming to have a look-see this afternoon. Hope it's an easy fix. Strange that both motors exhibit the same issue.....