Yanmar 2GM Running Rough, Stalls below 2k RPMs

[H33CRich]

This weekend opened a new adventure for the admiral and I; sailing to the slip with engine. We chose to do this for two reasons; one - I could not get the RPMs low enough to feel comforatable entering the slip; the wind was perfect and I got some dock help once I arrived. The issue is with the Yanmar 2 GM 15 HP just not running right. My guess is that I need to replace the primary fuel filter (increased RPMs could boost the mechanical pumping of the secondary on the engine). I was running late to head out of town on a business trip, so I did not get a chance to pull the filter (in the original filter canister from yanmar) once I got to the dock. If others have had an issue like this and it turned out to be a plugged fuel filter, then getting a new filter and purhaps cleaning the tank out would be the way to go. The boat was run sparingly over the past 3 years, was on the hard last year, and run for only a few hours in the previous season. Not exactly best case for diesel fuel conditioning.

 

[Steve Dion]

Rich:

Normally the issues with filters occur at higher RPM's (not lower). If your filter is blocked then it is starved for fuel at higher RPM's.

I would guess that you may be having an air leak would be my guess. Have you messed with any of the fuel lines recently. Those banjo washers can cause problems if they have been tightened and then loosened and reused.

 

[kloudie1]

Weak lift pump, air in the HP injector lines. valve clearances too tight

 

[Ken1686]

Had a similar problem with my 2QM15 a couple of years ago. The primary filter cartridge was clogged. Pulled it out and replaced it with a new filter cartridge. Engine idled fine after that. The old cartridge can be cleaned with kersone if new filter is not readily available.

 

[H33CRich]

Good info. I will replace the filters (primary and secondry) first plus pump out the fuel tank. If that does do the trick, I will look into the mixing elbow. The engine is cooling fine with a good discharge rate.

 

[H33CRich]

Ssaturday Update: After pumping out 15 gallons of black bacteria laced fuel, scrubbing with a long vent brush to all the areas I could reach through the fill hole, rinsing with 3 gallon of clean fuels, replacing the 10-micron filter on the engine, flushing the primary filter with diesel, wiping and cleaning the primary filter canister (black sudge, bacteria), adding 7 gallons of clean (bio fungal treatment added), repriming the system (took a while since I found the manual lever on the lift pump late in the evening), I felt I was getting closer but not there yet. Exhausting and messy day.

Sunday: After more manual pumping the lift pump and bleeding the air through the air bleed screw, I was able to get the engine started and run at 1000 RPM while in the slip. Still not idling great so I left it run at 1000 rpm for a while. Occasionally the RPMs would raise to 3k then back down below 1k rough and then raise back up to 1k. Then decided to go fo a sail. Enough of the fuel fussing and hoped I could just keep it running at 1k and in gear. Took the admiral and daughter out for a sail at 11am; good day for it with the sun finally braking through and a 12-15knot wind go SOG to 5.8knots with just the 150% genny. Came back in at 4pm, cranked the engine up and ran her at 1.5K back to slip. After docking, lowered the engine RPMs to idle but it did not die this time. Idled well. Perhaps the fuel issue is behind me for now. During the offseason, I may have to pull the tank out and really clean it out.