Yanmar 2GMF seized. How to troubleshoot?

[Pizzazz]

OK, so I took the engine apart (top part and oil pan only, enough to take the pistons out, all done in place) and discovered that the crank pin bushing on cylinder one cracked and the injector on cylinder two gave way (the rods holding it are slightly bent and it came off lose+there was oil around it, while the injector on cylinder on cylinder one was dry). Now the crank shaft turns freely.

My take is that the engine hydrolocked and the weakest components gave way. The question now is how to proceed. I found a guy at the marina who fixes engines and he can lend me all sorts of tools that I need to measure tolerances of the cylinders, crankshaft, etc. The common consensus is that the crank shaft on these small engines is quite strong and unlikely to be bent.

Question 1: What caused the hydrolock (I am pretty sure it was oil locked not water locked). Could a faulty injector seep oil? Could a leaking high pressure pump mix oil and fuel? How do I test the high pressure fuel pump?

Assuming reasonable explanation of the hydrolock and given that the rest of the engine looks in great shape, I am thinking of the following approach:

1) Check piston rods, cylinders, etc. for tolerances. I expect all will be good.
2) Replace the bushings on both cylinders
3) Replace the rings on both cylinders
4) Test and most likely replace both injectors
5) Send the head to a machine shop to check, clean and do a valve job (local $120)
6) Order new gaskets and put the engine together

Is there anything else I should preventively replace at this stage? The high pressure fuel pump is an obvious candidate but it is expensive. I am reluctant to pull the crankshaft because it would be hard to do in place and the timing/shimming stuff scares me. May be just replace the gear cover gasket. The engine definitely seems salvageable and the projected costs so far are reasonable but I am still thinking about going to a new engine.

Pizzazz

[four winds]

That looks like clean fresh oil. Had you just changed the oil?

You had the injectors out, but still took considerable effort to turn the crank. Correct? Then after the rods and pistons were removed the crank spins freely. Truly freely? Crank and bearings probably OK.

Pistons and cylinders wall condition? Major scoring?

Maybe an oil control rings failed. Not much space in that combustion chamber. Unburned fuel and oil might fill it fairly quickly.

Or fuel leaking to crankcase might overwealm a worn oil control rings. Is there fuel in that clean looking oil? How much oil or oil/fuel did you drain out?

What about that mucking around on the muffler repair? Could something there have restricted exhaust flow? worsening over the ten hours of running?

Bit of a mystery. Oil and fuel swamping the chamber, while being exacerbated by restricted exhaust?

Gradual seizing. Pistons trying to gald themselves to the cylinders or gradual filling of combustion chamber?

Check the rods carefully.

Lots of questions, no answers here. Just trying to promote the thinking process.

[Pizzazz]

Dears,

I completely disassembled my engine and now I am faced with the decision to rebuild or buy a new/used engine. The issue with my current engine is that when the piston rod bearing failed (likely due to oil starvation caused by leaking gaskets) it scratched the crankshaft. The crankshaft is now being repaired and there are two options, either it could be ground down a little then polished to fit a new +25 oversized bearing (available from Yanmar) for about $100/two days or it would have to be built up then polished and hardened to spec for about $400+three weeks. A new crankshaft is $900 and there is only one available in Kobe, Japan + two months shipping. Otherwise the engine is good shape but old. The hours are unknown, it says 1,500 hours, with records showing from 900 hours to 1,500 hours between 2006 and 2017. I believe it could have been rebuilt in the mid-nineties based on extrapolation or the hours may be actual. Cylinder walls and head tolerances are nearly to original specs. The rest of the engine is in very good shape according to the shop. I estimate the rebuild will cost around $2,000 in parts and shop time for the valve job/cylinder honing and I am excited about doing the rest myself. It is a challenging project and a learning opportunity.

At the same time, I could get a new 2YM15 for about $5,500 to which I can bolt my old transmission. The engine will fit with relatively little modifications but my shaft and propeller will move back about 3" (there is enough space but it will be closer to the rudder and it may affect handling in reverse). Then I am thinking I could sell the existing engine for parts and fetch at least $2,500 for the heat exchanger, head, block, mounts, injectors and pumps (may be this is optimistic?). So, the net difference is not that big and at the end of the day, the cost is really not that important relative to the overall cost of maintaining the boat. I know it looks a bit unreasonable to have a brand new engine in a 33 year old boat but hey, it is my boat and I intend to keep it. By the way, I do not want to go used because of the unknown condition.

Question is, what is the logical way to go? I feel I would feel more secure making extended trips with the new engine at least initially and I kind of like the new controls. On the other hand there is some sense of challenge and pride to fix the old engine, though there are other things that can fail along the way. Lastly, there is the question of time. The new engine looks like a two week project while fixing the old engine will likely extend well into August cutting from the sailing season.

Thank you for your responses and advice.

Happy sailing.
S/V Pizzazz

[sainted]

Whoo, boy. If you are going to keep the boat, get the new engine. I don't know how thorough the machine shop was in its inspection, but there are quite a few other parts that are lubricated by engine oil, including the camshaft bearings, that might have been damaged by lack of oil. You should also consider that other expensive components, such as the injection pump, are likely 30 years old. The new engine will almost certainly perform better than the old, and last but not least, it will be warrantied!

Good luck either way!

S

[Three Sisters]

Adding 3+ inches to the space between the stern tube/shaft strut and propeller hub is an invitation for vibration. Anyway, good luck with the rebuild.

[Wotname]

Originally Posted by Pizzazz

Dears,

I completely disassembled my engine and now I am faced with the decision to rebuild or buy a new/used engine. The issue with my current engine is that when the piston rod bearing failed (likely due to oil starvation caused by leaking gaskets) it scratched the crankshaft. The crankshaft is now being repaired and there are two options, either it could be ground down a little then polished to fit a new +25 oversized bearing (available from Yanmar) for about $100/two days or it would have to be built up then polished and hardened to spec for about $400+three weeks. A new crankshaft is $900 and there is only one available in Kobe, Japan + two months shipping. Otherwise the engine is good shape but old. The hours are unknown, it says 1,500 hours, with records showing from 900 hours to 1,500 hours between 2006 and 2017. I believe it could have been rebuilt in the mid-nineties based on extrapolation or the hours may be actual. Cylinder walls and head tolerances are nearly to original specs. The rest of the engine is in very good shape according to the shop. I estimate the rebuild will cost around $2,000 in parts and shop time for the valve job/cylinder honing and I am excited about doing the rest myself. It is a challenging project and a learning opportunity.

At the same time, I could get a new 2YM15 for about $5,500 to which I can bolt my old transmission. The engine will fit with relatively little modifications but my shaft and propeller will move back about 3" (there is enough space but it will be closer to the rudder and it may affect handling in reverse). Then I am thinking I could sell the existing engine for parts and fetch at least $2,500 for the heat exchanger, head, block, mounts, injectors and pumps (may be this is optimistic?). So, the net difference is not that big and at the end of the day, the cost is really not that important relative to the overall cost of maintaining the boat. I know it looks a bit unreasonable to have a brand new engine in a 33 year old boat but hey, it is my boat and I intend to keep it. By the way, I do not want to go used because of the unknown condition.

Question is, what is the logical way to go? I feel I would feel more secure making extended trips with the new engine at least initially and I kind of like the new controls. On the other hand there is some sense of challenge and pride to fix the old engine, though there are other things that can fail along the way. Lastly, there is the question of time. The new engine looks like a two week project while fixing the old engine will likely extend well into August cutting from the sailing season.

Thank you for your responses and advice.

Happy sailing.
S/V Pizzazz

I hear you regarding wanting to rebuild the existing engine, there some joy in rising to that challenge

However the two things that would persuade me to get the new engine is:

1. The unknown aspect of the past history of the old engine, even a very good rebuild can never take into account all the unknown past wrongs that may have taken place.

2. You are starting off with a clean slate. You know exactly how the engine will be cared for from zero hours. You get to be in charge of following best practices regarding the regular maintenance of the new engine. You can keep an accurate log book. You can keep it squeaky clean and in general, you will know it's entire history at any point in the future.

As for putting a new engine into a 33 year old boat, don't give it a moments thought. Engine do wear out, they are replaceable items and just like an old house may need a new kitchen or bathroom, so does an old boat needs new stuff every now and then. If do you ever want to sell the boat, having a current model engine that is clean enough to eat you dinner off, complete with accurate log book and full history will a huge positive in making a timely sale.

If it was me, I would pull the shaft, inspect it and have it shortened. Yes, more money but the engine (new or rebuilt) is only as good as the weakest link. It is also a great chance to properly check the shaft bearings and seals etc.

Rather than taking pride in the challenge in a once off rebuild, take pride in the ongoing challenge of keeping the new engine all shipshape and Bristol fashion. Friends will look at your "new" engine and (engine compartment) in years to come with envy.

[Captsteve53]

There's a lot to be said for a new engine and all the previous posts are good input re the other concerns with your old engine that said a couple of points to note:
1) Nothing wrong with grinding the crankshaft down in size it's absolutely common engineering practice and the crankshaft will be as good as new(depending on the shop quality that is)
2) Try to stay away from crankshaft build ups -this is really only for shafts that are out of production or very prohibitive in price/other -again building up really needs a quality shop that knows what they are doing and even then failures occur due to the stresses involved with the process.
3) If the shop has checked the camshaft/bearings and hopefully crack checked the crankshaft/con rods etc and given the all clear, then with a hone, rings and bearings(perhaps new pistons) and a head job all should be good
4) I would take the time to have the injector pump/injectors checked/replace the oil and water pumps, so after all this the new engine may look financially a better way to go
5) With these smaller engines they almost never wear out but fail due to corrosion/failed ancillary items/leaking gaskets/seals etc,

The new Engine Way:

1) Pushing the propeller back three inches is not the way to go with out checking bearing locations/hull prop clearance etc as there's engineering formula on these distances(especially shaft protrusion from P brackets or hull to the prop).
2) Therefore you should really have the prop shaft cut back the three inches and coupling re attached to bring your shaft back to original tolerances checking prior that the original tolerances are correct,
3) consider new engine mounts and shaft coupling along with a gear box check and as a minimum replace the gearbox input and out put seals as i have seen numerous failures after being fitted to a new engine

Cheers Steve (Lloyd's Maritime Small Ship Surveyor)

[Cheechako]

For $5500, new engine. Sell parts off the old engine and maybe get $1000 back?

[Pizzazz]

Dears,

An update on my seized 2GMF engine. As impatient as I am, I ended up with two engines, two gearboxes, two of everything... so, my crank shaft turned OK, at .25 undersize and I ordered .25 undersize crank pin bearings. The new parts look absolutely amazing and I am now rebuilding the engine, it should be ready by the end of next week. Est. cost of repair $1,200.

Meanwhile, I sourced a used Yanmar 2GM20F ($2,800) which looks great and runs great. Which one should I put in? Most people seem to think that the +3 hp of the -20 engine is worth it but I am attached to my rebuilt engine with every part measured and polished to spec. These engines actually are not that difficult to work with once you read the service manual a few times.

If anyone in the LA area needs a used Yanmar engine, I would be happy to hear from you. Otherwise, I will keep the second one for parts.

[Cheechako]

Well, assuming your crank isn't really .25 undersize ! (.025?) Maybe keep the rebuilt one. You know what you have. Although the rebuilt motor might be easy to sell, I wouldn't do it until you have used the used one for a while if you go that way.

[four winds]

.25 mm most likely.

[jamhass]

How "completely" and carefully did you do the rebuild (did you carefully inspect the cylinders, new rings, redo valves, inspect the cam lobes, oil pump, etc etc)?

If a careful and complete rebuild, I would go with that and store/dump/scavenge the other engine.

If a cursory rebuild, flip a coin.

[Pizzazz]

Quick update and closure to my issues. I got a second hand Yanmar 2GM20F and replaced the engine. Someone said it was a drop-in replacement - yes and no, had to re-adjust throttle cable, change over the transmission to the existing one - takes a couple of days. However, using the boom to lower the engine was super easy, a 15 min job.

I am rebuilding the old engine (2GMF) now. Not sure why but it is a great learning opportunity. However, it seems that these old engines are worth more if sold for parts than put together. If anyone in the LA area is interested in either the complete engine or parts, let me know.

Lessons learned:

1) Torque wrenches are great. Every sailor should have one one board.

2) Yanmar small engines are incredibly simple. Just read the shop manual and follow your instincts. If one carries key spare parts (injectors, high pressure pump, some bearings and a gasket set) it is totally possible to rebuild the engine under sail. It helps though to have it done once on land.

3) Engine maintenance is not just adding oil and water. The Yanmar manual says that every so many hours, bolts should be checked and loose bolts retorqued. I had my fuel lift pump totally loose and it was seeping fuel into the block. This could explain the engine spinning a bearing easily or it could have been just fatigue.

4) I went for a used engine mostly for the increased horsepower (16 vs. 13 hp). The Yanmar direct replacement, the 2YM15, makes only 12.8 hp. The 3YM20 would have been even better but it did not fit without shortening the shaft and that looked like too much of a hassle + costly with the sales tax.

Thank you all.

SV Pizzazz under way again.