Yanmar 4JH4-TE Catastrophic failure

[Ben51]

IMO the con rod bolt failed--just did. No specific reason, just chance.
On one of my two 4LHA 240HP, I had the exact same failure at 550 Hrs on the engine. No "events"--just chance.

Covered by warranty. As per Yanmar- "it happens"
I run my motors at 3000-3200 RPM. So my 550 Hrs at those revs probably equal yours at 1200-1400.

[Wotname]

Originally Posted by Hunterdog

So...how would one detect this, so I don’t get stranded again and destroy another engine?

The picture of the turbo changes everything. Up to this point, my assumption was the engine had been maintained and operated correctly and thus the catastrophic failure was due to a most unusual and unique event.

Clearly there has been a previous maintenance and/or operational problem. Without much more historical data, it is only a WAG to speculate of what that might have been.

I do not have much turbo experience (none on boats I have owned, some on friend's boats). However I would have expected your turbo as shown to be completely ineffective. I would expect there to be a definite loss of top end power and distinct lack of turbo noise when advancing the rpm up to the upper end of the power range.

I would expect to hear the turbo wind up even when advancing the throttle to max rpm in neutral and the lack of the whine would have indicated a turbo problem.

These things would be an early warning of developing problems.

But once again, I don't have hands on experience with operating this engine so the above may not be factual. It is after all, speculation on my part.

[Alita49DS]

Spot on Discovery15797. So the OP has a nine year old boat. Yanmar are unlikely to be interested and there is no warranty. Inherent defect? Where was the boat bought as the applicable law will have to be applied. The burden of proof will be in the OP. Against whom? There will be no contract with Yanmar. Does the vendor still exist? With any money? Bean feast for lawyers and experts all at the expense of the OP. Probably with zero chance of getting anywhere with kit that old.
Sh*t happens. That is why you pay for good insurance. If you don't adequately insure then look at yourself before trying to find somebody else to blame.

[jacktheflyer]

The con rod broke. It's a huge stretch for me to say hydrolock.[/QUOTE]

Fair comment and one I can't answer. However if you look at the pictures the rod is bent an not broken. The piston is smashed and the big end bearing is torn apart.

I would hypothesise the piston stopped suddenly either seizing in the bore or hydro locking and the momentum of the still rotating engine caused the subsequent damage.

Note the key feature in this failure is that the con rod is bent not broken. What can cause this?

[jacktheflyer]

Originally Posted by jimbunyard

Both valves are still intact and in the head, right?


Again, although the exhaust diameter recommended by Yanmar could certainly have contributed to the catastrophe, good luck making that stick.

Don't think you'll have much better luck with Beneteau, but they designed the exhaust...if you have or are putting a new engine in (couldn't tell from your original post), it surely seems that you should get a couple or three different opinions on the design of the current exhaust system.

Or it could have just been a fluke. What are the chances of it happening again?...

Good explanation. However I think the fluid must have been in the inlet manifold rather than the exhaust and the circumstances you describe fits what we know. having seen the picture of the turbo, I wonder if there may have been oil passing into the air side that accumulated in the manifold until the unusual attitude of the boat caused the fluid to run forward and get sucked into #1 cylinder. Works for me.

[rslifkin]

It's quite possible the rod was bent (and correspondingly weakened) prior to the actual failure. Once it's in that state, it's only a matter of time before something lets go.

[Wotname]

Originally Posted by rslifkin

It's quite possible the rod was bent (and correspondingly weakened) prior to the actual failure. Once it's in that state, it's only a matter of time before something lets go.

I would expect any noticeable bend in the rod would reduce the compression ratio to the extent that cylinder would not fire. Possibly a very small reduction in compression would only result in a failure to fire while the engine was cold but nevertheless, the engine would be running rough when started (and probably at all times) with a bent rod.

Of course I might be wrong...

[rslifkin]

Originally Posted by Wotname

I would expect any noticeable bend in the rod would reduce the compression ratio to the extent that cylinder would not fire. Possibly a very small reduction in compression would only result in a failure to fire while the engine was cold but nevertheless, the engine would be running rough when started (and probably at all times) with a bent rod.

Of course I might be wrong...

I'd expect the same. But I've seen enough cases of something seemingly working fine until someone goes to do maintenance on it and is immediately left wondering "how the heck was this working at all!?"

[Wotname]

Some of questions for the OP (to help our understanding of why the engine failed).

Any recent history of slow or hard starting?

Any recent rough running while cold?

Do you ever run the engine at or near max rpm (even for only a few minutes)?

If so, any noticeable loss of power over the last couple of years?

If so, when was the last time you heard the turbo whine?

[skipperpete]

That is one very sick turbo, this engine has been getting water into the exhaust scroll for quite a while. Absolutely YES this is an inspection item at the time of a service, it takes about 2 minutes to remove the air intake filter/screen and check the rotation , side play and end float of the compressor shaft. The frozen solid turbo would have been immediately apparent..... I’m puzzled why the engine wasn’t pushing out a lot of black smoke with zero boost.

[Wotname]

Originally Posted by skipperpete

......... The frozen solid turbo would have been immediately apparent..... I’m puzzled why the engine wasn’t pushing out a lot of black smoke with zero boost.

WAG

Perhaps the OP has only operated the engine at low rpm (???)

[Hunterdog]

Originally Posted by Ben51

IMO the con rod bolt failed--just did. No specific reason, just chance.
On one of my two 4LHA 240HP, I had the exact same failure at 550 Hrs on the engine. No "events"--just chance.

Covered by warranty. As per Yanmar- "it happens"
I run my motors at 3000-3200 RPM. So my 550 Hrs at those revs probably equal yours at 1200-1400.

9 year old engine...no warranty....right?

[Hunterdog]

Originally Posted by Wotname

Some of questions for the OP (to help our understanding of why the engine failed).

Any recent history of slow or hard starting?

Any recent rough running while cold?

Do you ever run the engine at or near max rpm (even for only a few minutes)?

If so, any noticeable loss of power over the last couple of years?

If so, when was the last time you heard the turbo whine?

NO
NO
NO
NO...I’ve only owned it for 18 months...
Now...this is the big one...cause I’ve rever really heard it. AND 99% of the time I’m running at 1400 to 1800 rpm.
I’m in no hurry, and don’t like wasting fuel!!
I run it up to 2600 rpm, just for 30 seconds once in a while just to see what top speeds are given how clean the bottom is etc...

[skipperpete]

Is it at all possible this engine was damaged and then repaired before you bought the boat? The guys who install your new engine will need to make absolutely certain that your exhaust and siphon break are to Yanmar’s requirements and functioning correctly, especially the vent loop. Incidentally, the siphon break is also one of the items on a normal service checklist, much more important than the turbo inspection.
Pete.

[a64pilot]

Originally Posted by Wotname

The picture of the turbo changes everything. Up to this point, my assumption was the engine had been maintained and operated correctly and thus the catastrophic failure was due to a most unusual and unique event.

Clearly there has been a previous maintenance and/or operational problem. Without much more historical data, it is only a WAG to speculate of what that might have been.

I do not have much turbo experience (none on boats I have owned, some on friend's boats). However I would have expected your turbo as shown to be completely ineffective. I would expect there to be a definite loss of top end power and distinct lack of turbo noise when advancing the rpm up to the upper end of the power range.

I would expect to hear the turbo wind up even when advancing the throttle to max rpm in neutral and the lack of the whine would have indicated a turbo problem.

These things would be an early warning of developing problems.

But once again, I don't have hands on experience with operating this engine so the above may not be factual. It is after all, speculation on my part.

Would also smoke like a train pulling a mountain grade too with much throttle at all.