Is it possible to hydrolock running engine?

[svRaison d Etre]

Did you check the starter itself? I saw a electric starter that engage and part of the armature was spin off wedging itself against the casing and field

[OldGreyB]

" 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) "

"There are metal shaving by pinion gear in the sail drive housing."

If your transmission oil level was low in the SD50, plus the metal shavings indication, plus the not being able to fully turn your motor, there is a good case you have run the main bearing #53 dry and it has failed.

The Yanmar manual specifically states that a daily pre operation check should include the SD50 oil levels. Practically this is normally difficult due to the location of the dip stick and access.

So when you rebuild, do yourself a low cost upgrade, install an oil tank header, so you can see the transmission oil level daily. It is easy, use a 10mm 1.5 pitch brass nozzle, which you install as replacement to plug #40, some 10mm clear PVC hose and this tank. [google ebay for : 1pc white Plastic Motorcycle Petrol Fuel Tank For Mini Motor Dirt Bike] Mount where you can see it, half full the tank, and mark a "cold" line horizontally on the tank.
To set up, fill your drive as per the Yanmar instructions, then slowly top up the oil to the top of the drive at #40. Then attach filled hose with S/S hose clamp from the vented header tank. (Can be messy at this stage )

Links to CF thread on this subject: https://www.cruisersforum.com/forums...ion-93387.html

[Rumrace]

The expansion tank is what all sail drives have lacked. As the oil heat it expands. Can’t go anywhere so it leaks. As it cools I sucks water it which boils. An expansion tank ends all this but it does expose hypoid oil to air with humidity in it. A friend put a desiccant bag inside you dry in the microwave. Down side is the absorb some hypoid stink. Its a fussy an oil as engine oil and much more fragile. Castrol made a series of hypoid multigrades which maintain their hydraulic character in typical heat ranges. If the house isn’t damaged it was the best part to break. I’d chuck the whole thing. I’m sure the gear has been past it’s no go point the bearing may appear ok but it’s done. Not having to move the engine forward is a win. Just slipping the bellhousing forward on the four bolts leaving 1/4” of thread retaining the part.
I’m not suggesting it but an example of a hypoid multigrade is 80/90. I used this on moog steering racks, stern drive hydraulics , trim tabs, motorcycle fork oil. It typically out performs heavier weight oils recommended.

I’d consult ZF if there is a recommended multigrade. Not Yanmar the my assemble other people’s parts.

[Rumrace]

I’ve dealt with ZF for years they are a real sweet company. They make auto transmissions for Corvette and BMW I have one of their paddle shifters on a bmw. 2 clutch pack horse power robber really.
I’ve ordered a SeaRex off them expect it this fall. It’s their smallest SeaRex and the price of the prop made me hide the bill.

[skipperpete]

It sounds very likely that you’ve found the problem. You DO need to slide the engine forward on the beds to get the saildrive out and trying to replace that bearing in situ would be like trying to put your underpants on.... over your head. Hopefully only the bearing is toast and it didn’t spin in the carrier housing. Are the gears ok? Its also possible that the drive plate has been overloaded and damaged if the “seized input bearing” theory is correct. Any thoughts on why the oil level was low? Usually if the lower seals leak, oil comes out the dipstick pinhole as the case fills slowly with water. Good time to lap the cone clutch and check ALL the bearings and preloads.

[karwas]

Well it was the sail drive pinion shaft bearing that had seized. We can clearly see that the ball bearings are shredded. Seal looks outwardly good and there was just a small amount of sail drive oil in the bell housing. Looks like the majority of the oil escaped down the drive not forward. Luckily the housing does not appear to be damaged.

After checking the starter, just to be sure, we decided to pull the engine. Set up two 4x4s above the companion way and used a 2 ton puller/come along with an engine balancer. Spent a lot of time disassembling the companion way stairs to get clearance for the hoist wire. The engine separated easily and moved forward giving plenty of clearance. The pinion shaft just needed some light convincing with a hammer to push it out.

[karwas]

Originally Posted by 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/I...one_clutch.pdf

Unfortunately there is no way to remove pinion gear assembly without separating engine and transmission. The procedure you are referring to is about removal of clutch assembly, not a pinion shaft assembly. I did exactly this 2 years ago. This time I had to move engine forward.

Przemek

[skipperpete]

I’m glad you solved the mystery Przemek. Unfortunately this will be an expensive repair because the input pinion in the photo is badly spalled and most likely the mating gear too. The bearing may have spun in the carrier as well so replacement SD50 might be the path of least resistance..........or an SD 60 at about $5,000🤢[emoji848]

[skipperpete]

Oh, I forgot to ask, how’s the damper plate after the incident?

[Searles]

My bet is a dropped valve, remove rocker box ,check valve springs ,have seen this several times on alder rebuilt engines who didn’t replace valve springs and collets.⛵️⚓️

[Searles]

To late ,problem solved .⛵️⚓️

[skipperpete]

And in response to the thread title , yes! Of course it’s possible to hydrolock a running engine ....if water can enter the air intake either via a failed intercooler core or a misguided attempt to wash a turbo compressor without disconnecting the boost connection to the intake manifold. Precom chambers ( Cat) can also allow water directly into a cylinder if they crack or split .....and any engine with copper injector sleeves and O-rings is capable of allowing water ingress. There’s about 15 psi in the waterjacket to help it in on the intake stroke . Blown head gaskets mainly seem to be a risk after shutdown.

[dori47]

Ours stopped suddenly. The cut off link broke off and in the waves, it was flopping around and the engine thought we had pulled the cut off . Took a long time to find it. Everything else checked out, nothing fouled the prop, the filters were clean

[BayouSailing]

speaking to the title only; YES.
I have seen two engines hydrolock while running:
- one from a faulty fuel pump diaphragm (overloaded crankcase with fuel, so it locked beneath the pistons, not above. Or both, who knows? Crankcase ventilation could have sucked it to the top)
- one from an ass-wired seawater pump. Rather than change impellers (beneath the powerhead, required powerhead removal) on a very old Johnson Saildrive (basically an Evinrude/Johnson 25 or 35HP engine above a saildrive foot), someone instead installed a constant rate livewell pump for cooling. Old owner must have run hard because he exhausted all the fluid. Sold the boat, new owner gets the problem, can't sail, takes his wife for a booze cruise to celebrate the new boat (idles for HOURS), and Kablooie, locked her up. Exhaust flowed.
- actually, one more. Improper exhaust design on an engine install by a "big" yard. Ran ok, again, on the way home from the yard, all the way to the slip. But when they shut it down, hot water came back through the whole new engine fast enough to melt the yanmar plastic intake screen. Yanmar called it unwarranted toast; installer threw their hands in the air; we were able to pickle the engine, get it running, reconfigure the exhaust and move the wet muffler, and she's still running today.

[boat driver]

not a running engine- but sailing downwind-
depending on your engine design in boat, height of muffler.
engine fails due to a wave literally shutting off exhaust flow- then when next wave appears, minus the engine running pressure , the water cascades right into the open valves.
\when apart, see if any moisture inside.