Yanmar 2GMF seized. How to troubleshoot?

[Pizzazz]

Coming back into the marina tonight my Yanmar 2GMF suddenly lost power, rpms went down to 1,500 even at full throttle then stopped. I could not start it (starter relay will click, lights dim but no cranking). Had to come back under sail in 1.5 knots of wind .

At the dock, it appears that the crankshaft is seized. It will not bulge even 1/8". There appears to be oil coming out of the throttle lever that was not there before. The transmission seems to be operating as expected and the shaft is rotating freely. Recently I have changed the oil (approx. 10 engine hours ago) and mucked around with the muffler that was leaking. About a year ago I changed the exhaust elbow and hose.

To me it seems as if something major is blocking the crankshaft. Could it be a bent rod? I pulled the compression levers up no change.

What are next steps? Take out the injectors and check for water/oil? Start disassembling the head? I do not have much experience with diesel engines but will learn. Any help will be greatly appreciated.

S/V Pizzazz

[Wotname]

Sounds serious.

Was the low oil pressure alarm working when you last started it? If so, we can assume it was still working when engine failed so probably did not seize for want of oil pressure.

When did you last check the over temperature alarm? To do that you have to remove the temperature alarm sensor and place it is hot water etc. So unless we know that the over temperature alarm was working recently, over temperature may be responsible for the seizure.

Is the oil looking normal - quantity and colour?
Is the water level normal?

More experienced others will chime in soon but I guessing the head will have to come sooner rather than later.

[Dulcesuenos]

Great deal on a low hour 2gm20f on ebay from a marine seller with decent feedback

[Captsteve53]

As previous reply-did any alarms sound (temp or oil), these small Yanmar engines are raw sea water cooled (no heat exchanger), so it's really common for salt deposits to build up in the thermostat housing and thermostat failure/exhaust housings and cylinder head galleries causing over heat situations and possible seizure,

It may have only seized the pistons in the bores and crankshaft could still be in one piece, I would remove the injectors and pour in some diesel and let sit for a day then try to turn the engine over using a socket and bar on the front crankshaft nut(working back and forth gently). If this works you may be lucky and the engine will run but more than likely will burn oil from there on as the rings could have lost their resilience,

If you get it going investigation into working alarm sensors would be a must along with checking /cleaning thermo stat and housing- with these sea water cooled engines you can run a product called "Salt Away" through every now and again during the season which helps clear the salt build up and used regularly assists with new build up,

[model 10]

The bearings will be the first to go, not the pistons. In any event, the oil filter will be full of metal, so cut it open to check. Then buy the engine on Ebay

[Scaramanga F25]

Did you check for water in the cylinders?

[Captsteve53]

Good idea with checking the filter for particles but before condemning the whole engine just to elaborate on these types of failures,

It depends on what you find re the cause if it was an oil related failure then certainly the bearings would be a primary suspect , however

If it is a water cooling failure the pistons nearly always seize in the bore prior to a bearing failure as the bearings are still under lubrication pressure and no where as hot as the upper cylinder temps, where as the pistons expand with the increase in temp cause more friction lose lubrication and seize in the bore,

So if you can determine the cause it might help with the direction of buying that new engine - or not!

[deblen]

You report : Engine slowed down & then stopped.
You can't crank it with the starter.
You opened the decompressors

My educated guess:
No knocking or other loud mechanical sounds
so no broken valves,con. rods,pistons,etc.
Probably no seized crank or con. rod bearings-usually cause knocking also.
Probably oil pressure was ok then.

I suspect overheat due to cooling water overheat, which caused a piston to stick.This MAY have scored a cyl. &/or ruined the rings.

Another slim possibility is waterlock,though opening the decompressors should have cleared water from cyls.

Looks like the cyl. head has to come off. Fairly simple job-google it. Take lots of celphone pics as you proceed. Download a service manual.Buy a "valve grinding/top end gasket kit.

I could be wrong. Good luck / Len

[edelweis]

The GM20F is a fresh water cooled engine with heat exchanger not sea water cooled.
F in the model type indicates fresh water cooled.

[sazarac]

Originally Posted by Captsteve53

As previous reply-did any alarms sound (temp or oil), these small Yanmar engines are raw sea water cooled (no heat exchanger), so it's really common for salt deposits to build up in the thermostat housing and thermostat failure/exhaust housings and cylinder head galleries causing over heat situations and possible seizure,

It may have only seized the pistons in the bores and crankshaft could still be in one piece, I would remove the injectors and pour in some diesel and let sit for a day then try to turn the engine over using a socket and bar on the front crankshaft nut(working back and forth gently). If this works you may be lucky and the engine will run but more than likely will burn oil from there on as the rings could have lost their resilience,

If you get it going investigation into working alarm sensors would be a must along with checking /cleaning thermo stat and housing- with these sea water cooled engines you can run a product called "Salt Away" through every now and again during the season which helps clear the salt build up and used regularly assists with new build up,

The engine in question is fresh water cooled 2 gm 20 f.

[wcapman]

For what it's worth I had a 2GM seize under similar conditions when I bought my boat back in 1987. The diaphragm for the fuel pump had developed a pinhole leak and allowed diesel into the crank case. The engine lost power but kept running for a short while and then seized a bearing. The loss of power was probably due to loss of fuel supply or pressure. This overfilled the crankcase with diesel/oil mix, which did not provide enough lubrication for the engine bearings. Drain the oil and see how much you get out. You can also smell it to see if there is any diesel. Of course the high pressure pump could also have leaked into the crankcase. Your report of oil there is a bad sign.

I replaced the engine with a 2GM20F in '90 and have had no issue since.

Good luck with it. Hope it turns out to be something simple.

[sainted]

Hoo, boy. From your description, I'd have to say that this engine is done. If it seized due to overheating, then the pistons will have almost certainly been damaged (the skirts will be scored, so will the bores). If it seized due to lack of lubrication, the crank journals will be scored. In either case, you're looking at a complete rebuild, and the price of the parts alone will be thousands, not to mention labor and machine shop expenses.

It is extremely unlikely that the engine seized due to water ingestion because it was running at the time. You'd literally have to pour water into the air intake to cause a running engine to seize. Water leaking from a blown head gasket or cracked exhaust manifold would simply be pumped out of the motor as it ran.

I'd seriously consider that used motor on ebay. It's going to cost WAY more that $2K to rebuild your engine. I guarantee it.

How do I know? Not only am I a marine mechanic, I just spent about $10K on parts rebuilding my Yanmar 4JH3-HTE.

Best of luck.

S

[Pizzazz]

Thank you for the support so far. Some good and some bad news. By the way, this is the 2GMF engine, made 1982-85, I believe, fresh water cooled.

I can now turn the crank, with a wrench, and it requires a fairly significant effort. I took out the injectors, seem fine. There appears to be oil in the cylinders and the exhaust. The stern of the boat is covered in thick black stuff, I believe oil residue. I am fairly certain the engine did not overheat. There was just no warning of any kind.

Could it be something simple like a gasket or a blown piston ring? I draine the water, it looks yellowish to me but not sure if it is antifreeze or oil.

In any case, I am proceeding with taking the head off. The engine is a 1983 model, so if it cannot be fixed I would replace. Kind of bummer, though. It was running so well recently.

[wcapman]

The 2GM20F will be an exact drop in for the 2GM13. They were discontinued a long time ago and finding a decent used one is getting harder.
I reused the 2GM13 transmission but had it rebuilt. Kept every cable the same. The engine bed mountings will have to be changed if you opt for teh newer series of Yanmar. The HP increase is VERY noticeable.

[Wotname]

Originally Posted by Pizzazz

Thank you for the support so far. Some good and some bad news. By the way, this is the 2GMF engine, made 1982-85, I believe, fresh water cooled.

I can now turn the crank, with a wrench, and it requires a fairly significant effort. I took out the injectors, seem fine. There appears to be oil in the cylinders and the exhaust. The stern of the boat is covered in thick black stuff, I believe oil residue. I am fairly certain the engine did not overheat. There was just no warning of any kind.

Could it be something simple like a gasket or a blown piston ring? I draine the water, it looks yellowish to me but not sure if it is antifreeze or oil.

In any case, I am proceeding with taking the head off. The engine is a 1983 model, so if it cannot be fixed I would replace. Kind of bummer, though. It was running so well recently.

Well it does sound like a mystery. It is pretty hard to seize a simple diesel engine without either staving it of oil or overheating it.

What was the oil level and oil condition like now.

Please do keep us informed when you finally discover the root cause!