engine dies after 2 hour run

[fiddler17]

My engine did this for a solid year. Had many "repairs" until someone finally found pin-hole air leak in fuel uptake fitting at top of tank/tube. Replaced and not further problems

[sinnerman]

Originally Posted by Cpt Mark

the electric fuel pump is only for priming the engine. It is not used during normal operations.

It is energized all of the time the ignition is ON.

The M25 and M25XP engines do not have a mechanical "lift pump".

[ronjgarner1]

I had a similar problem which just started after 4 years of faultless service on my new Beta 35hp.

I also have a Racor 500ma Prefilter/water separator as well.

Engine cut out 3 or 4 times. I'd bleed it and it would go again for a couple of hours.

I tightened the brass T-screw on the Racor Cap. Problem solved.

My seal in the cap was OK. But you might want to check that as well.

[Ranger2727]

I had a similar problem of the engine cutting off on a Wester beak 30 and traced the problem back to a leaking O-ring on the Racore filter
, replaced the O-ring, never had an issue after that.

[Anchorage Frank]

Originally Posted by Russ

Re: Yanmar 3gm stops at random underway!
Air leak guaranteed. Yes check your vent first, it's easy. After that, it gets a bit harder. I have been there with my Yanmar.
First, wrap a small piece of paper towel around EVERY fitting from tank to engine. Running the engine may do it and show damp diesel on a section where the fitting is loose. Gotta remember the diesel engine SUCKS diesel so the air gets sucked INTO the fitting and for that reason you might see nothing even thig there's a leak. IF no luck this way, don't give up. You need to get a small pump and PUMP diesel through the system preferably staring at the tank end of the hose. This WILL show a leak if it exists in the system between the tank and the engine. Yes, I did ALL this to find my leaks (2) even though I have all copper flare pipe fittings!
PM me if you need more help. It isn't likely to be anything else (except the vent, Yes I had a spider web clog one of my vents once, too, same scenario engine running stopping, etc.

Thanks very much. I've been thinking along these lines, and your detailed process is going to be very helpful.

[Hudson Force]

If there is air entering the system from the tank to the Racor; then, air will accumulate and be seen present at the top of the Racor. If this had been occurring, then refilling the raycor void would have been necessary to restart or bleeding the air out if the air leak was after the raycor. You had not mentioned this as something you had done when restarting; therefore, I'd go back to the vent plugged or fuel supply restriction in the pick-up tube.

[Sailing Scooter]

I had some trouble with a similar thing motoring up the Malacca Straits a couple of years ago. After changing checking the fuel system multiple times with no luck, I happened to notice the large main negative cable connected to the engine was severely frayed so that maybe only 10% of the copper was still joined..
After about 40 mins the engine started again and motored into a marina..
I cut and replaced the negative cable and had no more trouble with the engine stopping. I'm thinking there wasn't enough current to keep in the fuel pump solenoid open and it shut off..
Now I'm no electrician but the frayed cable seemed to be the problem, so maybe check this out on your engine also.

[sailingchiro]

In single engine airplanes, we have fuel, fuel, fuel, air, mags.

In diesel engines in sailboats it is fuel, fuel, fuel, air, battery.

I had significant problems with my fuel system and most were sucking in air problems. My fuel cutoff valve was sucking in air. My pickup tube would pick up something in the tank that plugged the 90 degree turn at the top of the pick up tube and create a vacuum that would allow the Racor to suck in air.

I replaced the fuel cutoff valve and the Racor housing. If the paint on the Racor is flaking off, it will most likely suck in air. I then removed my tank and cut inspection plates at each baffle. I then cleaned the entire tank with scraping and completely cleaning the tank. Then I removed most of the fuel (left about 2-3 inches in order to flush the crap out of the tank) and purchased a high volume diesel pump (10 gallons/minute) from Harbor Freight with a Napa see thru filter. I polished the fuel and tank for 3 hours. Now, all fuel that goes into the fuel inlet is filtered. Knock on wood, both engines have not quit so far. I also use Power Service products for bug growth.

I feel for you brother. I have been there done that. Losing an engine in a critical move is very humbling. Try turning a catamaran on one engine with 3 90 degree turns with a 15-20 knot wind down the fairway. It ain't gonna happen.

One thing you might try is have a day tank that eliminates all the ships fuel components. If you don't have any problems on the day tank, it is your ships fuel supply. I kept a 5 gallon jug with a fuel line I could drop into the jug for temporary service if needed. It is funny, the "jug" never had problems. Go figure. I still keep a couple of jugs available for emergency use when traveling off shore. 10 gallons on one engine will take me 120 miles if no wind. Hope this helps.

[Hanksy]

Reasonably maintained stands out to me. Can you elaborate on this? Skipped a few filter changes etc?

As a elimination error I would swap the filters and replace the seals. Watch for the small O ring on the racor that often gets overlooked.

[Heidi-Ho]

Just a long shot, but had a similar experience in the Virgin Islands on a bareboat. It would run fine for a couple of hours and then die. If you waited a couple of hours it would start up and run again. Found out later that someone had changed the engine oil and put the wrong dip stick back in. The dipstick was too long so the engine was low on oil and overheated and shut down. Weird thing is we were not getting any alarms or warnings.

[Sailnav]

Everybody seems to focus on the fuel Intake.

I think you should also check the Exhaust.

When was the last time you looked inside your Mixing Elbow, just downstream from the exhaust manifold? On my Perkins engine, it was a very thick casting that looked fine on the exterior. But 2000 hours of running at less than cruising speed created a build-up of soot and rust on the Inside, such that it choked the engine's breathing.

After removing the Elbow for internal inspection, the problem was obvious: the 2-in.-dia aperture had been reduced to 1/4 in.

Symptoms similar to yours.

[flyingfin]

A diesel is easy to diagnose, either air or fuel. Find a mechanic with remote tank and fuel pump to bypass yours and see if you get the same response.

[Hudson Force]

Originally Posted by Sailnav

Everybody seems to focus on the fuel Intake.

I think you should also check the Exhaust.

When was the last time you looked inside your Mixing Elbow, just downstream from the exhaust manifold? On my Perkins engine, it was a very thick casting that looked fine on the exterior. But 2000 hours of running at less than cruising speed created a build-up of soot and rust on the Inside, such that it choked the engine's breathing.

After removing the Elbow for internal inspection, the problem was obvious: the 2-in.-dia aperture had been reduced to 1/4 in.

Symptoms similar to yours.

This one sounds likely too, 'especially if you're not collecting air in your raycor and not bleeding air in order to restart.

[Squanderbucks]

Cut to the chase. Instal one or more clear vinyl hoses in the fuel line system lines. Helps if you already have it setup with Flare fittings. I switched all mine over a few yrs ago just for ease of maintenance. Run the engines - hard for a while and have someone watch. I could tell with mine at the dock so could verify myself. You can see which segment is the culprit.

If you do choose to change to flare fitting be sure to ask for Push-Lok hose connections and you won’t need alll those hose clamps which can be a source of leaks on small lines.
I prefer SAE. Flare for 3/8” lines because they are actually bigger than JIC but overall it doesn’t matter.

[Anchorage Frank]

Originally Posted by Hudson Force

This one sounds likely too, 'especially if you're not collecting air in your raycor and not bleeding air in order to restart.

Thanks. Really appreciate the notion; I've never looked there.