Logo

Intermittent Rough running

FORD_5.0_OMC

New member
Hey guys,

I run FORD 302s OMC 2 barrel Holly Carb and POINTS with Cobra Drives. Sportfishing boat, so runs a lot of hours and is well maintained. But starting having issues at the end of last season that have me totally stumped, which usually doesn't happen.

The engine would randomly and intermittenty become rough and if idle was low enough shut off. When it first started it seemed to just be at trolling speed. It would then go away and maybe come back that trip, sometime not at all. If you tried to smooth it out when it was acting up, the RPMs would jump around and engine would be violent. Didn't seem to matter whether engine was cold or warm. Troubleshooted it for the last 5 remaining trips of the season, each time thinking it was fixed until it came back.

We burn a lot of fuel through the season so I don't thnk its bad fuel.
-At first it seemed electrical the way it was acting and I ended up finding my Coil to Points wire was slightly loose (Thought that fixed it, but ofcourse came back next trip, at the same time, checked points and condenser, which only had about 50 hours on them at the time and they were fine.
Next traced out the whole ignition circuit for loose or broken wires, grounds ect, all seemed good. It seemed to get worse and trips went on. Wouldnt happen more often, but when it did happen it was worse. Started to only happen heading back to the slip through the bridges and marina, which was not good. So started thinking it was a slow speed, maybe starving of fuel. Went on to put my back up new CARB on for the last trip of the season figured that was the issue, since it was 5 years old and ethanol, but the issue remains and even started up at higher speeds around 2500. At that point the freezing temps were here and the boat got its normal winter care and put away.

I now plan on getting back into it, will do my normal spring tune-up. New Plugs, Points, Condenser, timing ect. and see if any of them maybe were bad, or if i see something obvious on the plugs, but after that im at a lose.


Engine has 400 hours since professionally majored down to the Crankshaft. Everything new and cylinders boored.

Going crazy and if it continues im gonna have to start tearing apart... sticky valve or fouled something would be more consistent? Mechanical Fuel Pump 4 years old, but would also be more consistent.

I know this is very poorly written and rambling but its just me rackng my brain on all this. I am very mechanically inclined and know this engine in and out and am at a lose.


Anyone anyone have any ideas or thoughts, just looking for a path and a discussion.

Thank you all.
 
Back
Top