Yanmar 4JH4-TE Catastrophic failure

[billknny]

I consider the "overspeed" scenario total BS.

No marine transmission I am familiar with can "forward drive" the engine, the clutch slips if you should try. It is the reason that you do not sail with the transmission in forward and the engine off, the clutch wears out from constantly slipping.

I know telling you what it is NOT really isn't much help, but it's all I have.

[Wotname]

Originally Posted by Jim Cate

wottie, I find it hard to visualize sloshing forcing water back into a running engine, even at half speed or so.

I'd expect that in the event of the purported hydrolock there would be some bearing damage in the big end shell. Your insight about bending before breaking is spot on IMO... good thing to check on.

Over revving seems unlikely too, as these engines are governed, and I don't see the prop developing enough power to push it up to really high rpms, especially at only 12 kts or so (have we determined that it is a fixed prop?).

So, I kinda lean towards a latent defect but surely not convinced. A forensic look at the broken bits seems in order.

Back in my hot rod days I broke a few rods myself. Small block Chevy engines... we'd heat treat and then shot peen the stock rods. Made them a lot stiffer, but when they failed it was catastrophic. Had one that took out every moving part, all the valves, cracked the heads, tore up the block, broke the crank, oil pump, magneto drive gear... the only reusable bit was the injector fuel pump that was external to the timing cover and thus escaped the shrapnel. Came apart at well over 9000 rpm and put a temporary end to my racing.

Good luck to the OP... hope that you can get some compensation, somehow!

Jim

Jim, I concur it is stretch of the imagination to think cooling water would be sloshing about in the exhaust of a running engine but perhaps it might be possible depending on the size (and layout) of the exhaust system and the engine rpm. However if hydro locking is determined to have occurred then the most likely source of water must be that in the exhaust system.

It is unknown if the wave slide was a determining factor but it is hard to rule it out as a coincidence.

I confess to knowing very little about the "Dock and Go" arrangement of the drivetrain but I can't see it being a factor in the failure.

Would love to see some close up pictures of the damaged parts (including the piston top and the head)!

Maybe things are different in the USA but I can't see any way that compensation could be obtained on a 9 year old engine with 1200 hours regardless of fault.

[jimbunyard]

Further to this tale of wild-ass speculation, sloshing water and (probably misplaced) hopes for compensation...

Depending on the geometry and comparative directions of the wave and vessel track, if the wave height is such that it is several feet above the transom as it overtakes the boat, depending on the engine and exhaust system's design, water could be pumped very powerfully back into the exhaust hose.

Also, on some (if not all) internal combustion engines, there are points in each cylinder's 2 or 4 cycles in which a vacuum can be introduced into the exhaust stream. In low exhaust-velocity/volume situations, and under adverse conditions where external sea level and the seawater level in the exhaust system might momentarily equalize at a level higher than the level of the exhaust valves, the wave-pumping action in combination with the intermittent suction-phase of the combustion cycle causing water ingestion, and hence a broken rod, might, to some more libral fantasists, seem at least possible...

Add that to Yanmar's notorious oversizing (in my opinion) of its exhaust hose recommendations, in a perhaps misguided attempt at one-size-fits-all, CYA protection against excessive backpressure (instead of a proper case-by-case analysis) problems, and the scenario seems a bit more likely.

As regards 'compensation', seems I remember someone in a movie somewhere saying that "the greatest thing about living in the US is that you can sue anyone, anywhere, for anything you want". Doesn't quarantee that the compensation you recieve will be anything more than that you made your 'point'.

Perhaps better to chalk it up to Neptune, or Poseiden, or whichever god you choose (or even physics or fate [or is that the fate of physics?]), though a detailed analysis of Beneteau's exhaust system design could yield a pecuniary reward (though one more satisfying to some might be that a safer, more seaworthy design would result...)

Doubt Yanmar or ZF would do much more than laugh (hopefully to themselves) if you pressed them on it...

[Hunterdog]

Here’s a photo of the block with the rod wedged in. Haven’t gotten it out yet...

[RaymondR]

What is the maximum speed the boat can achieved under power in still water?

[Wotname]

Originally Posted by Hunterdog

Here’s a photo of the block with the rod wedged in. Haven’t gotten it out yet...

Thanks for the photo!
Was the piston in a thousand bits or a couple or ....?

[olaf hart]

Originally Posted by jimbunyard

Further to this tale of wild-ass speculation, sloshing water and (probably misplaced) hopes for compensation...

Depending on the geometry and comparative directions of the wave and vessel track, if the wave height is such that it is several feet above the transom as it overtakes the boat, depending on the engine and exhaust system's design, water could be pumped very powerfully back into the exhaust hose.

Also, on some (if not all) internal combustion engines, there are points in each cylinder's 2 or 4 cycles in which a vacuum can be introduced into the exhaust stream. In low exhaust-velocity/volume situations, and under adverse conditions where external sea level and the seawater level in the exhaust system might momentarily equalize at a level higher than the level of the exhaust valves, the wave-pumping action in combination with the intermittent suction-phase of the combustion cycle causing water ingestion, and hence a broken rod, might, to some more libral fantasists, seem at least possible...

Add that to Yanmar's notorious oversizing (in my opinion) of its exhaust hose recommendations, in a perhaps misguided attempt at one-size-fits-all, CYA protection against excessive backpressure (instead of a proper case-by-case analysis) problems, and the scenario seems a bit more likely.

As regards 'compensation', seems I remember someone in a movie somewhere saying that "the greatest thing about living in the US is that you can sue anyone, anywhere, for anything you want". Doesn't quarantee that the compensation you recieve will be anything more than that you made your 'point'.

Perhaps better to chalk it up to Neptune, or Poseiden, or whichever god you choose (or even physics or fate [or is that the fate of physics?]), though a detailed analysis of Beneteau's exhaust system design could yield a pecuniary reward (though one more satisfying to some might be that a safer, more seaworthy design would result...)

Doubt Yanmar or ZF would do much more than laugh (hopefully to themselves) if you pressed them on it...

A displacement hull going that speed is also going to squat, so it’s a safe bet the water level was well over the exhaust outlet.

IIRC my old 4JH manual mentions something about having an external flap valve over the exhaust to prevent backflow.

Agree the 3” exhaust is a PITA.

Our V40 had the 4JH installed in Turkey, half way through a circumnavigation, replacing the original Perkins. They installed a sort of dry stack exhaust, with no water lift muffler. A big dry stack loop going all the way up to the deck, then water injection at the bottom of the loop and a straight run to the outlet.

Works OK, sounds like a semi trailer, but takes up a lot of space in the engine room and it’s impossible to work on the engine if that thing is hot.

I guess not having a muffler full of water is a good thing, but I often wonder how this exhaust affects our risk of backflow.

[Hunterdog]

This is an original Beneteau installation...nothing modified.

I’m not totally clear on the mechanics of the exhaust: but isn’t there a “box” of some sort in between?

[malbert73]

No way over speed did it for all reasons above. As another data point I did same thing on my T40 with my old Yanmar 4jhe motorsailing downwind on Atlantic off of NJ, running around 1600rpm. We surfed numerous times between 10-14 knots and never an issue with engine running.

[sailah]

Looks to me like a bent conrod, overspeed theory I don't think fits. Looks like a hydrolock, surprised that could happen running at 1400rpm

[Ghostrider421]

Funny how Perkins, Lehmans managed to live as long as they do/did. Problem today is cheaper materiels and labor costs. Volvo learned the hard way. I have dry stacks on mine, which after 10,000 hrs on the 4-108's is giving way to a pair of 40hp Tohatsus. I need the space.

[mvweebles]

This was not due to some sort of over-speed condition. On occasion, diesels 'runaway' where they get all the fuel they can consume and over-rev beyond redline until the fuel is shut off, the air is shut down, or something breaks - usually a rod due to bearing failure. It takes some period of time at redline RPMs or above for this to happen. 12-kts of boat speed ain't gonna do it. Your engine was either weakened at some point due to low oil or over-heating, or there was a manufacturing defect in the con-rod. If you care to do an autopsy, check the lower end bearings on the con rods.

As an observation, not that it makes a lot of difference in my opinion, but when I looked at your Navionics speed track, I noted speed was very low just prior to it being very high. Wonder if this was less a function of actual change in boat speed and more a function of losing and regaining GPS fix and doing a quick TxS=D calculation with compensating errors.

Regardless, sudden failure of a con-rod is a sobering story for a guy with a single-engine trawler.

Peter

[Montanan]

Reference Yanmar warranty.

https://www.yanmarmarine.com/theme/y...MPE-EN0034.pdf

[seabreez]

Originally Posted by Hunterdog

Good input. I have the broken parts. Maybe I should open an investigation?

I have seen engine failure of this type because the oil rushes forward and raised or goes up due to the curvature of the oil pan and hit the connecting rod and it was too much for the rod to displace all the oil in it's path. Very common in racing engines... that is the reason some engines have splash pans under the crankshaft bolted to the main caps to redistribute the oil evenly and prevent the oil from hitting the rods in motion. Some oil pans also have a baffle crossways with a door, to permit oil to go rearward and closes with gravity when the oil rushes forward. … my two cents worth... Roger

[bongo]

Following seas can cause overspeed conditions even on big ships. As the swell goes by the engine will lug, and then will race. The governor, under normal circumstances, reacts and keeps the engine/propeller at acceptable RPM. Ships, in addition to the speed limiting governor have an overspeed trip, which will shut everything down ASAP in the event the RPM still rises too high. I’ve seen this come into play 1) when the propeller comes out of the water, or 2) when the propeller shaft breaks. (Yes, I’ve seen #1 many times, and #2 once). A prime mover can overspeed immediately when it is loaded and then suddenly unloaded.