Stuck diesel genset has me stumped

[sanibel sailor]

I am helping a friend with his 78 foot motor yacht. She was involved in hurricane Ian in Fort Myers. Took on some water but not to the level of the engines or generators. She was tied up starboard side to and so the port side was exposed to wind and waves at the worst of the storm. Main engines and the starboard genset run fine. Port GEN set is stuck. It is a 20 kW Kohler with a 4 cylinder diesel.
I assumed a Hydro lock from waves making their way in the exhaust. I can rotate the engine backwards slightly but it has a hard end point in forward. I pulled the fuel injectors with no improvement. I was puzzled. I pulled the valve cover and all the valves move freely. Depressing the valves while trying to rotate the engine doesn’t seem to improve things at all. This didn’t make sense. Next I pulled the exhaust hose off the muffler, and was surprised to find it was dry. So it’s not Hydro locked. I guess that explains why my Hydro lock fix didn’t work.

So what could it be? I can rotate the engine backwards about 3/8 of a revolution to a hard stop in forward another hard stop. Not like a soft stop from compression. If it turns it’s not seized. I wouldn’t think a locked up starter or gear driven water pump would act like this. The genset ran fine the day before the storm.

What’s my next move?

[rslifkin]

Just to confirm no water intrusion, have you checked the oil level to make sure it's normal?

[team karst]

sounds like something hard went into the combustion chamber. Did you eliminate rotor to stator foreign material (FM)? Gens have lots of cooling air access/holes,slots. Hurricane winds can really make stuff travel weirdly.

[danstanford]

Got me stumped but hoping you share the findings in the end. I would think something in the combustion chamber would let you rotate much farther in the opposite direction to the one that gave you the 3/8 turn.

[skipperpete]

Hi Sanibel sailor
This sounds a bit like the third engine on the forum with a quantity of detached carbon in either 1 or two cylinders that actually stops the piston going over TDC. You could try to blow out the cylinders with compressed air but because it’s a precom chamber engine the results may not be a clean cylinder..... it might help to remove the glow plugs.
The first and second threads described these exact symptoms and the first guy removed the head and confirmed it was carbon that entered from the valve ports but while the second thread had the same symptoms that OP abandoned the forum before posting a follow up.
Failing the “Thick carbon” theory it could simply be a ring of corrosion in the upper cylinder and you keep hitting that corrosion but have free movement when the piston moves downstroke. Upper cylinder corrosion is quite common in engines with wet exhausts.
Also , take off the rocker shaft and check for a possible stuck exhaust valve.... be careful with the stem caps. If none of the previous suggestions works, I’d take the head off and try to rotate the engine again.
Pete.

[team karst]

The decision might be whether to slide the generator off the shaft, or to pull the head off the engine. The gen is around 200lbs, but might be easier than a head R and R.

did you look into the cooling slots for FM?

[sanibel sailor]

Originally Posted by team karst

sounds like something hard went into the combustion chamber. Did you eliminate rotor to stator foreign material (FM)? Gens have lots of cooling air access/holes,slots. Hurricane winds can really make stuff travel weirdly.

The gensets were not running. I cannot imagine anything other than water making its way in to the combustion chamber. Engine oil seems fine.

Actually, turns out it is Hydro locked. I was showing the owner it wasn’t, when it spit water out of the injector hole on 2 cylinders. Still having trouble getting it to turn. I sucked as much water out of it as I could with a cordless vac. Shop vac started smoking when plugged in. Another Ian casualty. If the injectors are out, shouldn’t that decompress the cylinder and let it rotate?

[sanibel sailor]

The cooling slots are hard to see but I didn’t see anything in there.

[sanibel sailor]

Exhaust valves depress easily. So do the intake valves.

I tried pressing the valves when it’s at the hard point hoping to blow any water out the manifold, but didn’t have any difference pushing on intake or exhaust valves.

[Jammer]

Try to get all the water out. Use compressed air or put a clean hose down into the cylinder and suck out the water with a mechanic's syringe or a shop vac.



Then squirt some oil ( 1 TBSP each or so) into each cylinder. The cylinder walls are likely somewhat corroded from the water. It doesn't take much. The oil will help the rings move past the corroded area more freely.

If at all possible get a socket and breaker bar on that harmonic balancer nut and ditch the slip joints. Then you can rock back and forth more effectively. Just work it, barely hard enough to move it a little further each time, once the oil is in, you'll get it.

[Uncle Bob]

And when it is all done and running perhaps a valve in the exhaust lines of both gensets, seal the pipes in times like those that caused the problem?

[sanibel sailor]

Well, the plot thickens. I have come to found out that someone came aboard during the storm and started the generator to run the pumps as the batteries were dead. There may be a bent rod or something. I’ve contacted somebody to come and pull the cylinder head in the next several days.

[RaymondR]

Piston stick from corrosion at TDC or BDC.

[Jammer]

Originally Posted by sanibel sailor

Well, the plot thickens. I have come to found out that someone came aboard during the storm and started the generator to run the pumps as the batteries were dead. There may be a bent rod or something. I’ve contacted somebody to come and pull the cylinder head in the next several days.

Your friend may find that they're better off replacing the entire genset (or at least the engine portion) if it's really that bad. New Kohler marine gensets in 20kw are $15,000. The industrial version of the crate engine that size sells for about half that but the marinized, generator-specific version will be way more. If there's a bent rod the genset can still be sold for parts which will bring the net cost down.


My advice would be to limit expenditures to basic diagnostic measures.


If insurance is involved your friend might want to get a surveyor out before disassembling anything.