How many is too many hours on a Yanmar 2GM?

[Martkimwat]

Don't know about the USA but her in UK long toothed Yanmar 1gm10s a 2gm20s are pretty common and spares are still readily available. In fact I believe that you can still buy new 2gm20 here, certainly 1gm10s. my friend has just bought a new one for his Hunter 26. In general, I have always understood that most marine diesels are good for around 10,000 hours with a major service/overhaul at 5,000 hrs. I fitted a secondhand 2gm20 into my 26 footer about four years ago. it had about 5,000 hours on it. I did a thorough top overhaul on it, before I put it in the boat and it has run as sweet as a nut since. Starts instantly, even on an undersized start battery (55 Amp hour) and at pretty well idle throttle. I have just changed it to a closed loop cooling system (external heat exchanger) as I want to install a calorifier at the end of the year as I organise about 6~8 rallies per year for two Yacht Clubs and one class association and boiling lots of kettles to wash up the cutlery and 'crockery' after, is a pain. Getting back to the Yanmar engine, the only weakness, is the original exhaust stub, which can corrode through and allow water back into the exhaust port and can corrode through into the oil gallery. it's not the end fo the world though as it can be re-sleeved with a 5mm wall stainless steel insert pushed in. The 'prevention' is to get a stainless steel exhaust stub which lasts much longer. They are pretty well bulletproof engines, second only to Bukhs.

[Cheechako]

There are quite a few used 2Gm's around and on Ebay. Many are asking $4500 US etc for them, which I think is way too high. I think someone has one FS here on CF for something like $2000.
But at any rate, they are available if he buys the boat and figures he must change eventually.

[cadmus]

2GM is a great little 13HP engine. I assume you mean the 2GM not the 2GM20.

They are really easy to rebuild. The 2GM had cylinder liners which made them very easy to rebuild.... below deck even... no rebore ever needed. (note the 2GM had cylinder liners. The 2GM20 or the 2GM20F did not). 2GM was raw water jacket and that scares some people.... understandable. But they last a long time. Sadly, Yanmar stopped making parts in 2020 or 2021. Quite a run... 1984 to 2020. If i could find a new head I would rebuild the one in my garage. It died because someone let it sit for 12 years, not because of failure. You can also HAND start them if you have the crank that fits in the camshaft knobbythingdinger (needs to be very well tuned and you have to have quick access to the compression release levers. Debatable practicality).

I suspect the high resale value on ebay is just because the cheap ones sell fast and the expensive ones sit. I know, because I was watching the prices on ebay and craigslist for some time. But they also hold value at >1800USD because many dyedinthewool old school salty tech-curmudgeons find this to be a simple little bombproof engine. The 2GM has a following.
If yours is running I would suggest you might enjoy it.
If you like the boat, do not let a running 2GM stand in your way. It might outlive you.



Non-OEM and OEM parts were quite abundant 2021. Maybe not everything.



Note the following if you buy it: I was told by an experienced tractor mechanic (and some dude online) that the main block is shared with a tractor model engine. On the main block but opening into the front end assembly, starboard side, is a little plate sealing off a 3" hole (i can send photos). This is a hole for what was a hydraulic pump on the lawnmower/tractor. It meshes to the cam shaft gear. I always wanted to hook up a little hydraulic pump there. Never did. You should. Tell us how it goes.

[wingssail]

My 3JH has 6835 hours and runs reliably, starts instantly, no smoking, good oil pressure, and no obvious problems. We've had a couple of scares about the engine but in the end, after extensive analysis and inspections, decided the engine was fine. We've had no rebuilds or major work other than a rear main seal replacement which we did ourselves (in the cabin).

If your engine is well cared for I don't see any good reason to replace or rebuild until needed. (if you were venturing out to cross oceans then maybe a new engine would be advisable). As for resale value, the amount you spend on a new or rebuild will not be recovered when you sell. It may make selling your boat easier but the value will not increase by the amount that you spend now.

Look for weak parts, corrosion and rust. Upgrade any suspect exterior parts and have the top end serviced, but the basic engine might just be fine.

[drdoyle]

The heat exchanger and pumps will be the biggest headache. Some engines have proprietary cast iron expansion tanks combination exhaust manifolds that are not available anymore. If you buy the boat at a reasonable price just run the engine until it becomes unserviceable. Depending upon your abilities as a mechanic a simp,e older diesel is very rebuildable.

[Capex]

FWIW as a surveyor, I have seen a 2GM with 12,000 hours logged on the clock, previously used on a charter boat before needing an overhaul. I have never replaced an anode in a Yanmar engine as, unlike converted industrial engines, they are built as a marine engine. The beauty of the 2GM is the fact that the engines can be started even if the battery voltage has dropped to 11 volts, just by starting cranking with the engine decompression levers open. Good luck with a great little engine.

[cdy]

$19K ? Too much money especially with such a used engine
Maybe 12K to 14K - but not sure where you are located - in Florida thats a $12K boat at best unless pristine

[AA3JY]

Could be one hour or couple thousand hours depending on how the engine was maintained

[sailorboy1]

Originally Posted by AA3JY

Could be one hour or couple thousand hours depending on how the engine was maintained

I bet high hours engines are more about luck!

[SuW]

Originally Posted by OldManMirage

... I just paid 13K for a 1980 Endeavour 32 with much less hours on the engine and Mack sails with a Mack Pack on the main were one year old. Just my opinion.

That's a great find! They are really nice boats!

[lituya1617]

I had a 2GM29F in my 32' sailboat. It did not run when I got it. I rebuilt it with $1200 worth of parts (complete overhaul: new bearings, pistons, rings, valve job, new valve seat, seals and gaskets. It took a week to do it right. I also replaced an external oil tube, fuel pump, and cleaned the injectors. I have no idea how many hours were on the engine; however, the ring ridge in the cylinders was hardly worth reaming so it was not a very used up engine. The major reason the engine was not able to run was from corrosion. One exhaust valve seat was so rusted it had to be replaced and there was a lot of deep pitting in the cylinder heads. I traced the rusting to the fact that the engine was using a water lift muffler, much like most yachts. This allows water vapor and salt to enter the combustion chambers when the engine is turned off. If an engine sits with an exhaust valve open for a long time, like this one did, the water will rust the devil out of the head. Other damage was harder to analyze. There were pits in the rear main bearing, large ones, but there was no water in the oil. I buffed out the pits a bit and calculated that there was ample bearing surface left so I did not have to get another crankshaft. It ran perfectly (started immediately after the overhaul) and got absolutely wonderful fuel economy. My little boat ran along at 6 knots and got more than 24 miles per gallon - better than my truck! I love this little engine and I believe it will go 20,000 hours if properly set up and maintained. I would NEVER use a water lift muffler because that exposes the internal working parts of the engine to steam with salt in it. A hot exhaust is easy to construct and a regular muffler is just fine. One advantage of having an above-deck exhaust is being able to see the gas and know the engine is running cleanly. I could not hear my exhaust over the sound of the engine so they are quiet. If you want to know how good the engine is, pull the head and inspect it. A ring ridge that protrudes 0.005 into the cylinder indicates the rings and other parts are pretty worn. The good news is that these little engines are really worth an overhaul. A new engine will set you back $7,000 and the new designs are not going to match the endurance
of the old ones. Parts are still available because these engines were used in Yanmar and John Deere tractors for decades.

[Mediaguy]

Have you thought of doing a compression test....Maybe that would answer your question.