Hydrolocked? Yanmar 4JH2-TE

[Wotname]

Another left field guess.
Is there any chance the boat was struck by lightning during those two weeks?

[IsaakOker]

Originally Posted by unbusted67

Well, wait. Then that's your answer. Don't pull the engine. Just pull the trans.

I just had a similar problem on a volvo MD17C and I wasn't able to get it going again. 12k for a new motor. yay.

Ohh dear.. Well I hope it doesn't get to that sum here. 😢

I've tried everything on this engine and until I don't pull the engine out and take the transmission off I won't be certain nor believe it could be that.. Haha

I have to take engine out anyways so its coming out and I hope I'll manage tomorrow. Should though as the head is off already

[IsaakOker]

Originally Posted by Wotname

Another left field guess.
Is there any chance the boat was struck by lightning during those two weeks?

Nope, no chance.. I've been on it nearly 24/7.
What would lightning do to the engine? Melt it? 😮

[a64pilot]

Very unlikely, but it could spot weld parts.

I’m surprised many don’t think fresh water rusts high carbon steel, for anyone who has ever rebuilt engines, a degreased cylinder bore can rust overnight, not heavy rust, but definite rust, handle one and you can see fingerprints rusted into it tomorrow.
Leave a car out in the rain for a couple of weeks and see how bad the brake rotors rust, we didn’t drive the Miata for a couple of days and when I released the parking brake, the pads popped when it first moved, they had rusted to the disks.

[IsaakOker]

Originally Posted by a64pilot

Very unlikely, but it could spot weld parts.

I’m surprised many don’t think fresh water rusts high carbon steel, for anyone who has ever rebuilt engines, a degreased cylinder bore can rust overnight, not heavy rust, but definite rust, handle one and you can see fingerprints rusted into it tomorrow.
Leave a car out in the rain for a couple of weeks and see how bad the brake rotors rust, we didn’t drive the Miata for a couple of days and when I released the parking brake, the pads popped when it first moved, they had rusted to the disks.

OK, yeah no lightning but I still don't think that the rust is enough to avoid me being able to turn over crankshaft.

I didn't know that a fingerprint will do it but I suppose sweat is salty..
I do expect freshwater and humidity to rust carbon steel fast but to an extent that you can't get undone? Specially in just a few weeks?

I mean, I do see, without much knowledge that the bores have been seized up before at different spots or at least close to being seized but still..

Anyways, let's see tomorrow without gearbox.. The only last answer after the gearbox is to turn the engine around 🤔

[Wotname]

Originally Posted by IsaakOker

Nope, no chance.. I've been on it nearly 24/7.
What would lightning do to the engine? Melt it? 😮

Originally Posted by a64pilot

Very unlikely, but it could spot weld parts.

......

Yeah that was what I was thinking especially taking into account the starter motor has also seized or gone short circuit in the same time period.

IsaakOker, I note you have said you do marine electrical work so forgive me if you already know this - a stalled (or stationary) starter motor presents an almost dead short to the battery. This is a function of all series wound DC motors. It is only when spinning that the motor limits the current flow (and the current flow is proportional to the torque developed). This suggests your starter motor is either mechanically seized (somehow) or has a short circuit winding.

[Wotname]

Originally Posted by a64pilot

........

I’m surprised many don’t think fresh water rusts high carbon steel, for anyone who has ever rebuilt engines, a degreased cylinder bore can rust overnight, not heavy rust, but definite rust, handle one and you can see fingerprints rusted into it tomorrow.
......

Yeah I guess it can rust fast and I note that an engine sitting for 5 years probably had very little oil still on the bore but it didn't rust up in five years, why in two weeks. Going by the youtube video, the engine was only turned over for 10 seconds and that is hardly enough to fill the water lock and have it come back up to get water into a cylinder or so I would have thought - been wrong before though

I guess we will find out soon enough!

[sailah]

I agree I know how fast rust can form but this just seems unlikely to lock up that solid after such a short time. Leaning on a 6' cheater pipe to the point you're rounding over a crank bolt? I'm suspicious that rust is the real culprit. Plus coolant won't rust as fast as water.

But I hope I'm wrong and we get a good answer.

[a64pilot]

The coolant most likely there from removing the head, more often than not you get some coolant in the bores even with the coolant completely drained.
A good proper mix of coolant is actually pretty darn good at preventing rust, not perfect, but much better than pure water.

[IsaakOker]

Hii Everyone!

Just a quick update although no clarification yet 😢

So I've been testing the starter and yes, I have to rewind the starter, etc so I probably will buy a new one as the solenoid is also gone.

As for the locked up engine, I've tried to take of the gearbox from the shaft coupling but I will have to cut the 4 bolts loose so not that far yet. I might take it off the engine first though and deal with the shaft coupling later on.

The result of testing is.
In neutral, I can move the shaft easily with bare hands.
In gear, I can also move the shaft although need to use a spanner but can also move it fairly easily. As many turns as I like.

In BOTH cases, the engine crankshaft & pistons don't move.
Is this normal or is this showing either an engine output issue or the gears in the gearbox seized?


PS, I think that the coolant in the bores was from removing the head as it wasn't a lot and I removed quite a lot before I took it off.

[boatbod]

If you have eliminated the transmission as a possibility, and physically removed the starter motor (eliminating the possibility of a jammed pinion), your only remaining cause must be a seized engine.

[IsaakOker]

Originally Posted by boatbod

If you have eliminated the transmission as a possibility, and physically removed the starter motor (eliminating the possibility of a jammed pinion), your only remaining cause must be a seized engine.

I haven't removed the transmission possibility because I don't know if the shaft should move having it in gear when the engine is locked up..
I would have though that if the engine is seized, the transmission output or shaft shouldn't move when in gear but only in neutral & in this case I can move the shaft both in gear and neutral.

Also, I'm having issues with bolts as they're either too corroded or rounded so I can't get the gearbox of the engine nor the shaft coupling of the gearbox..

[a64pilot]

Depends on the type of transmission, some it’s entirely normal to move in gear but with resistance, and those types I believe are the ones Yanmar warns against sailing when in gear as you will damage the transmission.
I think those may be cone types and I suspicion that when engine driven the cones are forced tighter together and usually don’t slip, but when driven form the driveshaft, they can slip and this slipping will cause failure.

Long story short I don’t believe you have a seized transmission since it rotates freely in neutral.

[Geoff54]

Originally Posted by IsaakOker

The result of testing is.
In neutral, I can move the shaft easily with bare hands.
In gear, I can also move the shaft although need to use a spanner but can also move it fairly easily. As many turns as I like.

Sorry I've been busy.

So, it depends on which transmission you have.

If you have a KM4A, that has a cone clutch and it is normal to be able to move the shaft while in gear, although if it moves too easily there is probably some wear on the cone.

If you have the other type, KBWnn (i forgetthe number), it has a multi plate clutch. I don't know this trans but I don't think there is any "automatic" engagement, so I wouldn't expect that you could turn the shaft in gear. But I'm not 100% sure.

The model number is on a plate on the gear housing, on the back IIRC.

And yes, if you have a KM4A, you should sail in neutral and let the shaft spin freely, so that it doesn't wear the cone.



Good luck.

[Geoff54]

Oh, and the coupling is usually an interference fit on the trans output flange. Even after the bolts are out, it can be a ***** to separate them. Be careful not to bend the flange. Let me know if you need and information on how to do that. And if you are using PB Blaster or similar, keep it away from the output shaft oil seal - depending on the seal material, the penetrating oil will "eat" the "rubber".