View Full Version : Marine Power 350 efi

Sea Scouts - S. Florida
12-07-2010, 05:15 PM
I Skipper a BSA Sea Scout Ship in S. Florida and oversee a fleet of boats for our region's squadron. One recent donation to our organization is a 1997 MAINSHIP 31ft. Sedan Bridge with +/- 370 hrs on the engines. She carries two MarinePower 350EFI.*Would someone shed some light please on the following: Port and Starboard engines both start and idle very well at temp. +/- 150F, cruise temp. +/- 162F. My port engine cuts out after 15-20 mins at cruise 2200rpm. No stutter no cough just dead....! Will not restart immediately but does so after maybe 20 mins. this has happened three times already, we have had a friend mechanic diagnose with a computer and "all readings are per spec" says he. Short of swapping out parts until*I get lucky, any suggestions?*
Don't laugh but I recall that my old Dodge Dart*had a failing coil, after heating up she would cut out but *would restart once I cooled the coil with a rag soaked in cold water..... Obviously I do not want to try the same at sea on these fancy engines, but could it be the coil? Anyway to test!
All help appreciated
Boys Scouts America
Sea Scout Ship 814
Skipper Furlan
Cell: 954 5514068

12-07-2010, 05:50 PM
Check the fuel tank vents to make sure you don't have one clogged by a mud dauber. After that it surely sounds like a temperature-sensitive electrical problem like coil, wire harnass plug, fuel pump.

12-08-2010, 10:23 PM
The beauty of twins, is the ability to swap some components.... such as your ignition modules and/or ignition coils, and without too much trouble, and certainly with little expense!
If there is enough fuel line length, a portion of the fuel system can be checked this way also.

It can become part of your P of E.... (process of elimination)... one item, one item only at a time.
The P of E will never let you down if done systematically and thoroughly.

You'll find it, it just may take some fiddling around, and a few test runs.
Good luck.


12-09-2010, 01:00 PM
If each engine has its own fuel tank, I'd start with it. Check the vent per post #2. Two other items can cause these symptoms - dirt in the bottom of the tank blocking the pickup screen and an anti-syphon valve that is malfunctioning.

If both engines 'drink' from the same source, I'd start with the ignition system on the troublesome one, per Rick's post #3.

Sea Scouts - S. Florida
12-10-2010, 09:57 PM
Thanks to you all for the quick response.

I have since tried the engine and again the Port engine cut out at cruise same sit. as before. This time we pulled a spark plug wire and grounded with a screw driver on the block then tumbled the engine,,,,no spark!!!!!!!!

Seems to be electric then and associated to temperature...I am going to descale the engine (with a home made pump and barnacle buster) maybe it is a sensor otherwise I am guessing it is the coil....may either swap starboard to port and test or simply replace the presumably damaged one...

Will let you all know.

Thanks again!

12-31-2010, 12:02 AM
I have a Marine Power GM 5.7L MEFI-4. I have the same exact problem. I replaced the coil with the ICM and it did not solve my problem. I am still working on my issue and believe it is a sensor or the ECM. I have been troubleshooting this for sometime and am about to go to carburation. I am interested to see if you are able to isolate the problem.

12-31-2010, 08:49 AM
Does the engine have a crank sensor?

12-31-2010, 12:07 PM
Yes it does, and I have not replaced it yet.

01-01-2011, 10:49 AM
I would check that first.

02-05-2011, 12:55 AM
any resolution to this problem yet? i have the same issue and would appreaciate any ideas...

Sea Scouts - S. Florida
04-07-2011, 05:24 PM
Sorry for the delay in response. After descaling I was unable to resolve so I opted to change the ECM, the coil and rotor...she ran great at WOT for 20 miles...no probs at all. Then a copule weeks ago she failed again on the Port engine but at idle (would start fine) cuts out after 15 mins....engine is not heating up! I looked below the helm station thinking maybe a loose wire (can't see nor "feel" anything loose) nor is there any eveden oxidation. I then had someone have a look and his opinion is that the fuel is dirty he sees filth in the GEN SET filter that feeds off of the same tank. SO- this sat I am going to top her up with high test and use SYNTEK fuel additive (great stuff), put her to sea I hope to run about 100 miles round trip and that that would clear up any filth in the tank. Boats - or Lord!

04-11-2011, 03:00 PM
If the fuel and tank are "dirty", best to remove and replace it, especially with the ethanol variable.

"Polishing" fuel has been common for fuel oil installs for a while and is relatively 'new' for gasoline. I'm not conviced there are any OTS chemicals that can 'restore' fuel that is contaminated or degraded.

May also want to get a fuel pressure gauge and a test light to monitor the fuel pump....those pressure control switches seem to have a high failure rate.

Sea Scouts - S. Florida
04-11-2011, 07:34 PM

I'll begin by saying thanks to all for response and suggestions. I believe that I have resolved my challenge, following are details:
Last Sat. we put to sea for an intended 100 mile trip we completed 80 miles. Prior to leaving I replaced port engine fuel filter - I neglected to replace Starboard filter due difficult access. I applied 5 oz. XFT (double dose treatment) at fuel top-up. We had 100 gals old fuel some of which was several years old...and 100 gallons fresh fuel 89 Oct. ($5.50/gallon - on the water cost). I carried four spare fuel filters on board for the trip. Result: First leg (At 3000 rpm) at six hrs. starboard engine stuttered and coughed then lost speed then sped up etc. etc. for maybe 3 mins. then shut down. I replaced starboard fuel filter, she stared up immediately and we ran both engines 3000 RPM for a further 2 hrs no problems. Next morning for a further 7 hrs. back to home port. (Engines ran smooth as silk).
I believe that the residue build up (varnish) and other accumulated filth, because I ran her long and hard, and with the movement at sea - was pulled into the filter to the point of starving the starboard engine. I will again replace both filters and once more top up, I expect only good things!
I am happy to give details on the product if needed.

Again thanks for the assistance

Sea Scouts - S. Florida
04-11-2011, 07:35 PM
Please have a look at the note below, i have I believe finally resolved the issue. let me know if you want to try the same product!