Yanmar 4JH4-TE Catastrophic failure

[Hunterdog]

Nice. Good advice.

Yes, I remember in engineering school (many years ago...ahem) mutilating a variety of materials. The charpy impact tester was one of my favorites. Then looking at it under the microscope....fun.
I’ll take some better photos tomorrow and post them.
Will see if there’s a materials place on this island.
In the mean time, here’s a photo of better days in the recent passages:
Flying downwind from Sardegna to Menorca...
And anchored off isle lobos...where I caught perfect wave for a week.
Thanks

[ChrisAndLenore]

Previous owner of our boat had the same exact experience.

The "rogue" wave hit the transom hard enough to force water through the exhaust system and into the engine (in seconds). The first cylinder with an open exhaust valve threw a rod.

The exhaust now has a flapper over it to prevent a reoccurrence.

Chris

[bclaude]

The head of YANMAR Technical support for Spain and Portugal is hernan_zwolinski@yanmar.com. He is very competent and helpful. He helped me through a difficult warranty claim back in 2017. I suggest you reach over to him directly. He is the go to person for dealer to approve warranty claims.

[wingssail]

While hydrolock seems like the most probably cause it is amazing to me that the exhaust force of a running engine could allow seawater to push backwards against it.

Our exhaust system has a 2" hose and rises four feet before dropping back down to a 1.2" outlet, which is 12' from the engine. The force of the exhaust shoots water out the stern about 8 feet. We have no flap on the outlet but we have a ball valve (at the high point inside the boat). However we have never closed that valve.

We have never had a case in which seawater pressed against the exhaust pressure and flooded the exhaust system while the engine was running. I don't know if this is due to the design or just luck.

If your engine and exhaust system permits this, I'd say avoid running the engine in heavy seas. I will say that we rarely are running the engine in big seas. If the wind is up we are sailing, however we will run the engine to charge the batteries. At 2000rpm (our charging RPM) then engine does produce a lot of exhaust flow. Whatever, it has not happened to us.

BUT, on three occasions we have had water ingress into the last calendar while the engine was stopped. The cooling water syphoned into the exhaust system. Twice this occurred before I installed an anti syphon loop between the cooling system and the exhaust. The third time (after 25 years), was Wednesday. After sailing for a couple of hours the engine would not start. It would not crank more than the smallest amount of one revolution. That sounded like hydrolock to me. After about four tries, it started and ran fine, but a LOT of water was ejected from the exhaust system. I suspect that the anti-syphon valve in the anti-syphon loop was plugged, but after running the engine the anti-syphon seemed to be functioning. There could have been another undiagnosed problem.

So what does this mean to any of you who stuck with this narrative this far?

Steps should be taken when designing or engineering an exhaust system.

• A flap on the outlet is a good is a good protection against forceful entry of seawater
• An exhaust system designed with a high rise and a limited diameter outlet to increases exhaust velocity.
• An anti syphon loop with an anti syphon valve or opening is needed to prevent flooding when the engine is stopped.
• Periodic maintenance of the anti syphon system is important
• Avoidance of running the engine in big following seas might offer some protection

[rslifkin]

High rise in the exhaust system is definitely important. On a sailboat, I think I'd also consider dumping the exhaust on the side and also probably at a downwards angle, rather than straight out the transom. That should make it harder for a large slug of water to get shoved straight up the pipe (regardless of engine running or not).

[Bilgediver]

Originally Posted by Hunterdog

Left Correllejo 3;30 am to make Morro jable, Canaria by mid day. Winds to be 18-25 kts. Swell 2m and decreases as we fall beneath the shadow of the fuertaventura. By 8, the sun just cracking thru the clouds, I handed the helm of the Beneteau Sense 50 to first mate Tracie, and my head hit the couch amidships. Winds 14 kts, 150 to 170 degrees off the starboard stern, and a following sea, we were making good time, averaging 6 kts. Autopilot requested some more battery, so 1400 rpm of the yanmar 4JH4-TE. I left it in gear as when I left the helm the speeds were down to 4 kts. A little extra speed would be nice to make anchor in day lite .
BIG BIG MISTAKE.
About 10 minutes later I hear a HORRIBLE winding noise as
the boat lunges forward...a rogue swell throwing us down a huge wave. We slid to 12 knots...
I shut er down, but it’s too late. After several sail-in anchorages, a few tows out, and finally ending up at Carzola, the Yanmar dealer in Gran Canaria. (I will write the riveting story of surviving the epoch Sahara sand storm of 2020, motorless, on 2 anchors later...see latitude 38, or follow us us on fb grateful sailor)
Bottom line...the #4 cylinder rod came off. Engine destroyed.
I just bought the new, improved 4J80 motor with a strait sail drive. No more electronics between me and the throttle. New motor has over speed protection built in.
After 100 years of motor-sailing...now?

I have 10,000 miles on this boat. Engine about 1200 hours. 2011 engine, with the dock and go system, which I have a love/hate relationship with. In oct 2018 left Turkey...

I feel that Beneteau, Yanmar, and ZF Marine produces an inferior product that would fail just running down a wave at 12 knots. Latent defect.
This is a massive safety issue...no?

Comments please:

As others have said , this is a diesel engine and if set to run at 1400 rpm then under normal circumstances the engine would be governed to this speed and the governed. Reduce the fuel to maintain a steady speed. However you say the boat lunged forwards and you hard the engine winding. I suspect you mean that the engine speeded up. What I think happened is that one ore more of your cylinders has worn oil control rings and the lunge caused a surge of oil in the sump with oil passing upwards in the forward cylinder. This might have resulted in oil getting past the rings into the combustion chamber causing the engine to speed up uncontrolled. If this did happen then maybe an inspection of pistons will real if one is much more oily than others.

I have produced this effect in an MGB sports car by excessive braking from high speeds however the oil just came out of the exhaust as smoke as not enough compression to produce the diesel effect.

[ChrisAndLenore]

I was also amazed that a wave could force water that far.

But a large wave could exert considerable force for 10 or 15 seconds given the right conditions. According to the owner, that's what happened.

Also, the original exhaust did not have a riser. The new system has a "Vetus gooseneck" that provides almost half a meter of lift right at the transom.

Between the riser and the exhaust flap, I can't see any water reaching the engine, whether it's running or not.

Expensive repair, regardless.

[Ncancro]

Originally Posted by Wotname

I think ReefM and Jimbunyard maybe on the money here.

Possible scenario - engine running at low rpm (1400), not much exhaust gas flow, cooling water pooling in the exhaust system and staying there until the exhaust back pressure builds up enough to push it out. Next lot of cooling water pools up but this time (at exactly the wrong moment), the stern picks up, boat starts surfing, gravity moves the pooled cooling water back towards the engine end of the exhaust. The wave possibly enters the far end of the exhaust and pushes the pooled cooling water far enough forward to hydrolock the aft most cylinder - game over!

Not saying this what happened but it seems feasible to me - a set of events that match the known facts. Of course there may be a another set of events that also explain the known outcome.

A close look at the conrod would be helpful. With a hydrolock I would expect the rod to bend before it broke. A latent defect in the rod should (IMO) show a developing crack face without any bend.

Hunterdog, was the broken rod nearest the flywheel? If so, in the Yanmar terminology, it is the #1 rod as the #4 rod is nearest the forward end of the motor (assuming no V drive).

It certainly sounds like a hydro lock based on the lowest cylinder being damaged and the steep angle bow down. There should have been enough exhaust pressure not to allow this though.

[RaymondR]

Originally Posted by Ncancro

It certainly sounds like a hydro lock based on the lowest cylinder being damaged and the steep angle bow down. There should have been enough exhaust pressure not to allow this though.

Even if water managed to find it's way back into the exhaust manifold of a running engine I can't see it managing to get back through the exhaust valve into the engine. The valves only open a small way and the gas expelling from the cylinder would blow it back down the passages in the head before it had a chance to enter the cylinder.

It's more probable that water has entered at some rime, partially hydro-locked and slightly bent the rod or started a crack in the piston or some other component, which has then failed at some later date.

[rslifkin]

Originally Posted by RaymondR

Even if water managed to find it's way back into the exhaust manifold of a running engine I can't see it managing to get back through the exhaust valve into the engine. The valves only open a small way and the gas expelling from the cylinder would blow it back down the passages in the head before it had a chance to enter the cylinder.

It's more probable that water has entered at some rime, partially hydro-locked and slightly bent the rod or started a crack in the piston or some other component, which has then failed at some later date.

That's definitely the more likely scenario, particularly on a turbo-ed engine. However, exhaust reversion can / does happen in some engines at low rpm / light load. There have been cases of gassers sucking water back when throttled down to idle too quickly if the exhaust system is poorly designed. I'd expect it's less likely on a diesel, as they're un-throttled, so they'll be pushing a larger exhaust volume at low rpm / light load than a gasser would be.

[Bill Seal]

Looking more closely at the first pictures, something beat the crap out of the head of the unbroken rod bolt and wallowed out the hole in the rod. I'd guess the cap came loose or off and the crankshaft crammed the rod into the head.
The turbo has several shiny blades just before the ones that are crammed with parts of piston, so I'd guess it was running just before the poo hit the fan (literally)

[argonauta1]

Max prop or other type of feathering prop is the way to go.

[col50]

The cylinder-head at #4 cylinder appears to be totally free of carbon.
This happens when small amounts of water repeatedly enter the combustion area, and is not caused by just one slug of water.
And then there is the rust on the crankshaft. Obviously water entering the cylinder over a prolonged period was the problem. How it got there is the puzzle.
I sure wouldn't run the new engine without some changes to the exhaust system.
Do I see crack in one of the valve-heads?

[DumnMad]

Hunterdog, Have you ever surfed in the breakers at the beach ?
You (boat) don't slide down a wave, you get pushed by the forward motion of the water at the top of the wave. When you are just in front of the wave the water is dragging you back towards the breaker that is about to overtaking you.
Your motor revved up when the prop was just in front of the wave as the water dragged back and the prop had nothing to push, then you shut it down at the critical moment when the water direction reversed and shoved from behind. Almost like you went from forward gear to reverse.

[Hunterdog]

First, a huge thanks to all. I really am learning a lot about these engines. And I am at a distinct disadvantage from a language perspective as so much is lost in translation.
Update, the new engine was delayed a week in Barcelona...ahhhh Spain;

Here’s some more photos of the elbow, and the crank bolts

And about the exhaust: It’s located on the Starboard side, fairly high above the water line. We were on Starboard tack when this occurred.