Is it possible to hydrolock running engine?

[karwas]

Hello,

I am writing this from the ocean, 30 miles from Moro Bay, so I will keep it brief.

Yesterday, about 2 hours after departing from Monterey and sailing
south in rather heavy seas (steep, short waves crashing on the stern)
my engine (Yanmar 4JH5E with SD50 saildrive on Beneteau OC45)
suddenly stopped without any previous warnings.

The water temperature was OK (~80C), there is a clean oil in the engine,
no indication of overheating or anything obvious.

Starter is not able to crank the engine. I have loosen the belt to eliminate
possibility that balmar alternator or water pump is blocking an engine
and still starter is not able to crank. The crankshaft pulley was able to
move maybe 1/2 inch, not more than that. But it does not looked like
a seized engine to me.

I suspect that pinion shaft on the SD50 saildrive got seized, and is
preventing the engine from cranking, mostly because the oil level
in the transmission was very low (below bayonet) but before I will
go anyfurther with disasembling saildrive I wanted to ask:

1) is it even possible that engine hydrolocked from while it was running?
2) is there anything else which could went wrong and I could test
in the ocean?

Thanks,
Przemek
S/V Festina Lente

[markxengineerin]

1) is it even possible that engine hydrolocked from while it was running?

I would say no, not via seawater through the exhaust, as the exhaust pressure is enough to keep water out. Especially if you have some sort of vented loop/ proper exhaust system.

I would try draining the oil/carefully cutting open the oil filter to look for metal debris. If you don't find any, very likely that the issue is in your drivetrain. I'm not familiar with saildrives, but if there's an easy way to disconnect it from the engine, that would be my next move, to see if engine then turns by hand. I would not be using the starter motor, just rotating by hand at this point.

[RaymondR]

A sudden engine stop without preceding noise is most likely a rope in the prop.

[Jammer]

If it went into hydraulic lock while running there would have been a really loud bang.

[StuM]

Originally Posted by RaymondR

A sudden engine stop without preceding noise is most likely a rope in the prop.

That by itself wouldn't stop the engine from turning over in neutral.

[thesaltytar]

Originally Posted by StuM

That by itself wouldn't stop the engine from turning over in neutral.

I'm not familiar with sail drives at all, but why would that prevent the engine from turning over in neutral? If the clutch is disengaged I don't see how any external drive issue would prevent the engine from starting at least.

I would be curious if the engine is properly clutched out and, assuming so, see if it can be barred over. Failing that I think the valve cover has two come off for a closer look.

[NPCampbell]

A blown head gasket can hydrolock a running engine but if your oil is clean then that most likely isn't the issue.

As someone above mentioned, if the engine was running and hydrolocked then the inertia of the piston and associated rotating masses won't like meeting an incompressible chamber and something is going to break or bend. Most likely a connecting rod. It normally makes a pretty good bang.

[skipperpete]

So is the coolant level ok now?
If the saildrive was low on oil the input shaft bearing would be a candidate for seizure. A shipyard here put a new engine package in a yacht but neglected to fill the saildrive with lube oil and it managed to go for 5 miles before it locked up. A new saildrive was supplied and the original saildrive was later repaired..... only needing two top case bearings.
Any clues as to where the saildrive oil leaked out?

[RaymondR]

Originally Posted by StuM

That by itself wouldn't stop the engine from turning over in neutral.

If it's a cone and cup transmission trapped torque might have it jammed in gear.

[Rumrace]

I got 5 bucks on a rope 75 cents on amazing Cali sea weed.
Put the motor in neutral. Rock the crack pulley with a big power Barr. I doubt it’s the Yanmar the sign off before breaking with lots of warning . You were not overheating which is the only way the engine would shut itself off.
The Sea Drive is also a ZF quality piece. Their flaws are expansion for hot oil. This can lead to oil seals going but usually inside the boat. Hypoid oil stinks and absorbs water quicker than any other lube but gets neglected while the motor gets pampered.
It’s key oil to maintain and for any of the various clutches used. Again their is no lay shaft in a seadrive. It’s a lot simpler than a stern drive but a much weaker clutch. Anything in a sea drive which could seize an engine would have got real noisy. Except a rope.

[karwas]

We made it safely to Morro Bay, where we were towed in, and are recovering after a long sleepless night of 30 knot winds and short interval 9 ft waves.

Thanks for all the great input. This is what we have found so far:

1. Engine will not turn over using the starter which appears to be due to excessive current load. No clunk, crunch, click on starter gear or solenoid.
   
2. Engine does not appear to be hydro locked. The injectors and combustion chambers are clean with no water and just a bit of oil and diesel.
   
3. Coolant is at same level as when we departed.
   
4. Engine oil looks and smells new as it was recently replaced.
   
5. Alternator and water pump spin freely with main belt removed.
   
6. With diesel injectors removed we can turn the crankshaft by 5 degrees to the left and right.
   
7. Were able to move the sail drive pinion assembly towards engine by gently hammering on the studs.
   
8. Pulled the sail drive clutch assembly. Everything on this assembly moves smoothly. Gears do not show wear and bearings are smooth. Can engage forward and reverse.
   
9. Propeller is not locked/jammed with line etc. as the sail drive clutch assembly was able to rotate, in place, before disassembly.
   
10. Sail drive pinion gear does not appear to move at all when turning the engine crankshaft.
    
11. There are metal shaving by pinion gear in the sail drive housing.
    

[Rumrace]

Sorry to hear. Are you on the dry yet.
If you were on Lake Ontario one of us would come tow you.
For rum
The good news is the clutch is intact.
Have you moved an engine forward before.
Is it time for new engine mounts anyway?
I have to read up on it. I’ve witnessed and assisted. A bunch of 2 x 4’s a chain hoist and two old heavy blankets.
Low oil or water absorption in oil appears to be the villain

[Rumrace]

HEY i just read how to change a 50’s pinion gear without moving the engine forward. The part you need are pretty easy to get.

https://www.plaisance-pratique.com/IMG/pdf/Yanmar_SD40-SD50_cone_clutch.pdf

[grantmc]

One possibility is a broken timing chain.

[Sailmonkey]

Originally Posted by grantmc

One possibility is a broken timing chain.

Nah….all gear, no chain.