Yanmar 3JH2E Stalling at Higher RPM Under Load


Jul 17, 2020
Hunter 376 Washburn, WI on Lake Superior
Hi all,

We're in process of transporting our new-to-us Hunter 376 cross the Lake Michigan and Lake Superior to get her home. The first 6 days/300 miles were great. Some sailing, a good bit of motoring, decent conditions.

However, the other day we ran into a bit of an issue with our 3JH2E while motoring, so are currently docked and trying to problem solve.

We were motoring into a pretty good chop on northern Lake Michigan for most of the day Wednesday. The motor ran great through most of the chop--I ran her at about 3000 RPM, it was bumpy but we pushed through as we navigated some of the shoals.

After a few hours we finally made our way through the Mackinac Straights, things calmed down on the seas, then the motor suddenly lost power, sputtered and died.

I put throttle at neutral, she started right up, put it back in gear, ran fine at 2000 RPM, throttles up to 3000 RPM, died again.

I started her again, started up, and we motored the last few miles at 2000 RPM no problem.

We spent a (planned) day hanging out at Mackinac island, I swapped the fuel filters (Racor 110 and Yanmar primary). Bled the system, started no problem. I ran her at 3000 RPM in neutral for a while, no issues

Filters did look a little dirty, although I wouldn't say they were really bad.

We departed yesterday, bow into the wind/waves again. We had no issue leaving the harbor, we got things set down below, then I increased speed. Again, it was choppy but not terrible, although we were bow in to the waves. After about 10 minutes she lost power and died. I started her up, ran her in neutral, no issue. Put it in gear, powered up, died.

At that point we put up sails and sailed back to Mackinaw City, as they had a diesel repair facilities. We had no issue powering into the harbor and docking, all at around 2000 RPM or below.

The diesel techs were unable to assist, but gave me the number for WW Williams. I spoke to Joe, who was graciously helpful. Shout out to Joe at WW Williams.

He suggested it may be a clogged fuel pick-up or one of the elbow joints before the Racor filter. He suggested blowing air through the lines and seeing if they cleared anything.

Last night I removed the fuel pick-up and manually blew through, it seemed open/clean. I couldn't blow through the fuel line (no air compressor and I didn't have enough lung-wind to push the fuel in the line back), but I did disassemble the Racor elbows and confirmed they were clear. The Racor did NOT look dirty, so I don't think it was a second clogged filter. I should note, this is a poly tank, so unlikely to have any rust floating around, probably just 20 years of crud.

I re-assemebled and checked the fuel vent. It seems to be clear.

I had started assembling a rudimentary fuel polishing system before we embarked, I finished this last night and ran it (accessing via the fuel gauge port in the top of the tank). It pulled up some gunk, but not any significant water or crud. I did let it run for a few hours, swapping the first stage 30 micron filters once an hour or so.

I bled the system, started her up, ran in neutral at 3000 RPM no problem, and ran her at 3000RPM in reverse for a bit (tied to the dock, so I didn't want to run too long), no problem. But, given that yesterday we ran for 10 minutes or so at higher RPM I don't trust this as solved.

We are going to take her out shortly and try again, but am posting looking to see if others have had similar experiences and what you found for a fix. We're a little nervous heading north to the St Mary's river (where we have limited ability to hoist a sail due to channel width and maneuverability limitations and will be motoring against th current) and/or Superior where we can sail but may be far between ports with the ability to source parts.

Additional theories:

Have folks had fuel lift pumps fail? Is this indicative of a failure?

Is there a way to tamp-down junk in the the fuel tank with out while "under way" (by under way I don't mean out on the lake but far from home).

Reading the manual it seems like a fuel supply problem (and crud in the supply feels likely as we had been running into choppy seas), but could this be a sign of an injector or injector pump problem?

Additional thoughts or troubleshooting steps?

Any thoughts are appreciated.
Jan 30, 2012
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Sounds like intermittent stirred up trash in the tank. If there are any coffee ground like flakes in the Racor beware. If you have an inspection plate have a look. Otherwise --

Did you check/change the motor mounted filter element? Also, if this Racor is a spin on (bowl and filter) check the head. There is an anti drain back under one of the plugs on top that will accumulate trash. While a rare occurrence there is a possibility of fuel line age any place in the (suction side) lines - those that run from the tank to the lift pump. If the lines are old they can collapse internally under sustained vacuum - but you will never see any symptoms except weird motor performance at higher motor loads. Maybe replace all of them - won't take long and pretty cheap too.

Good reason to consider a vacuum gauge. Pretty much takes all the guesswork out of fuel supply diagnosis.

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Jul 17, 2020
Hunter 376 Washburn, WI on Lake Superior
Thanks for the recommendations. Today we motored for 4 hours (another upwind day) but wave action was calm. No motor issues whatsoever, ran at 3000 rpm the whole way (even bumped it up to 3500 a couple of times for a few seconds to see if I could get it to stall out--no issue).

I didn't see any coffee ground like crud in the Racor either time. I cleaned the bowl the first time before putting the filter back in, I didn't see anything the second time. I did change the primary (on motor) filter as well.

Our air intake is in a box type mount on the motor. I opened it--there isn't any screen element, it looked relatively clean. Certainly not obstructed.

One theory I thought about today- the motor kill pull on this boat is quite stiff. It takes a surprising amount of effort to pull to the point to kill the motor. I wonder if it could have gotten stuck in a half way state (maybe by being kicked or bumped) where it was fine at lower rpm but restricting too much fuel for higher RPM. I don't know if they makes sense or if that is even a possible state/mode for they switch, though.

Tomorrow will be all motoring but on the St Mary'a, so presumably little chance of churning any tank sediment. Then on to Superior, where anything could happen!
Jan 1, 2006
Slickcraft 26 Greenport, NY
You can oil that kill cable. The most through way is to remove the cable from the housing - you have to disconnect it from the engine (This procedure was described to me in a Mack Boring Basic Diesel Maintenance course). But I've just oiled it from the pull button by pull it out and moving it back and forth on the theory that most of the corrosion will occur in that area. Use 3:1 oil.
We were moving a powerboat and had a very similar issues. We never really solved the problem. In calm water the engines would run OK. When it got rough they didn't. We were fueling every day so you would think the fuel was clean. But the boat had sat for an extended time and I can only conclude that there was crude in the tank that would overwhelm the fuel filters, which we were changing regularly.
For at least one engine there was a sensor on the fuel filter which was made of plastic. A mechanic told us that people tend to over tighten it and break or crack it. Then it leaks air and the lift pump can't make enough pressure to run at high speed. On those engines there were sensors for everything and when one got a sniff of something wrong, the engine would go into a safe mode. Even if you are coming into Charlestown after dark between two container ships.
For any delivery of a boat in open water I would beg the new owner to insist that the fuel be polished, including cleaning the tank before embarking on the delivery - especially if the boat sat for any more than a winter layup.