First time boat owner and I am...

[Stubie]

First time boat owner and I am hoping someone out there can help!  We bought a 2001 31 ft. Sundancer with 5.7 350's, the port engine had just been rebuilt, it had a little over 200 hours on it when it was rebuilt.  During the survey and subsequent sea trials the port engine stalled a few times when throttled down to an idle. We hired a Merc Certified Mechanic and have since replaced the IAC, had the ECM re-flashed, installed a new MAP sensor and it is still stalling.  The engine starts right up and idles great after sitting overnight; rev it up a little {2000 rpm's} and throttle it down to an idle; it spits, spurts and sputters then stalls.  I've put 25 gals of fresh fuel in along with couple Merc fuel additives.  Hoping someone has some ideas on what might be causing the problem. Thank you.

[GEORGE]

This may be the second time you've seen this, my computer did a dump....have you looked at the water fuel separator? Did the
tech do a code scan. I just replaced the IAC on mine today. I coded out but also caused the engine alarm to sound twice every minute. Because you still have a problem I am guessing the tech did not use a diagnostic tool/machine and took a guess on the IAC and the MAP. There could be a blockage in the air hoses coming and going to/from the manifold from the IAC.

[Stubie]

Thank you George for your response! The tech did pull all the codes, in fact has to come back with more sophisticated diagnostic equipment; sent the codes to Merc for analysis. I think it might be fuel related. It hadn't stalled the last time I took it out, so the problem may have been solved. Once again, Thank you!!!

[MedicRN]

Stubie: Port engine; change the fuel filter? $7.00 At higher RPM's, the fuel pump will pressurize the filter. Throttle to idle, pressure drops, engine stalls. See....everything else is working fine. When fuel sits for months during the winter months, the filters gum up. For $7.00 it should be standard new season list. Have a great summer.

[keokukone]

One other thing to check, the dip tubes into the gas tank may have filter elements on them. In a 16 year old boat, gunk can plug the sintered metal filter. Cuts out fuel flow at low rpm. Especially true when carburetor cleaner added to the fuel cleans the varnish off the inside of the tank.

[Stubie]

MedicRN

[Stubie]

Stupid question! Replaced the water separator fuel filter - is there only one on the port side? I have two separate gas tanks, doesn't make sense to have one fuel filter. Thanks!

[keokukone]

Sorry for being unclear. The filter elements are in the gas tank, at the end of the dip tubes, not visible . Follow the fuel line to the gas tank. Should be able to remove and inspect the dip tube.