Internal Mechanical Failure vs. External Impact? Severe Damage on Caterpillar 660 HP at Turbo Spool (No Felt Impact)

Is there any hull damage near the prop? These days I drive a 12 seat water taxi, in a fleet of 8 vessels. 5 round trips a day, 2 hours a round trip. We are getting a couple damaged props a month. An interesting lesson in mechanism of failure, I guess. My boat has a volvo penta outdrive with duoprops. I've had leading edge damage on the forward prop from something coming in from the front. Under acceleration the water from the lead prop isn't fully meeting demand from the rear prop, so on another occasion a branch or something got sucked in from the side, jammed between the props briefly, so the forward prop had a blade bent forward and the aft prop in the pair had a blade bent backward. And on the Yuwala (I think: maybe the Misty?) something just exactly the wrong/right size got jammed between the hull and the prop. Prop bent, shaft bent, stuffing box leaking bad, when everything stopped at once. On the travel lift the corresponding mark on the hull was obvious. No damage further upstream fortunately.
That was unnecessarily wordy. Too much coffee. And the OP has not replied with a set of photographs yet.
 
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montero said:
You wrecked the clutch after the impact.
The engine revved up and broke down.
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This is the kind of claim that would need a lot of physical evidence to prove. I believe there are several unrelated issues. Without looking at the physical evidence, a claim like yours would be rejected.
 
Dont know which cat but both the 3176 and c12 had a 660 rating, going to guess that its one of those engines. Both had a penchant for aftercooler leaks, could potentially have ingress on throttle up that locks up a cylinder early in the turbo cycle. Remeber a few guys having issues with that, although most had less catastrophic symptoms that caught the leaks. Some of the smaller cats certainly died that way spoiling water into an accelerating cylinder can make a mess.

Usually the vulkan coupling is the weak link in the drive train. Ive seen a crewman panic and shift from forward to reverse on a cable controlled boat, shear the main from the mounts flip it over, and have the shaft migrate forward into the gear case. Have seen more than engines lock up and tear a vulkan coupling. But to tear the vulkan, and still mess up the shaft, cutlass and prop... seems a bit of a stretch. Could maybe figure in a well undersized shaft and strut and bearing in a sportfish... but to bend a prop as well without a strike would have the overwhelming majority of folks thinking a strike.
 
You forget the broken engine mount and destroyed turbo.
 
Kinda. Soft mounts dont take a ton to break. Ingest water through a turbo from a bad aftercooler would explain bad valves/turbo/hole in the block and slowing down a main immediately from early turbo range all makes sense. Not a real shocker to see a torn Vulcan coupling, enough so that a few of us keep a spare aboard...

The hard to factor in part is a warped shaft, bad bearing, bad strut and bad prop from a rapid slow down. Could almost believe the shaft/bearing/strut as the sport fish world sometimes uses minimal saftey factor and some tiny diameter shafts. Killed a few Vulcan couplings, rarely is the strut/shaft/prop/bearing the weak link.
 
If the turbo was just starting to spool up, that is probably fast idle.
 
Yeah, not exactly break neck speed for a stop on a prop and shaft.
 
The OP has left the room. He probably did not find a story to justify his claim. In fact, he didn't even mention if there was insurance on the boat.
 
gonzo said:
The OP has left the room. He probably did not find a story to justify his claim. In fact, he didn't even mention if there was insurance on the boat.
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Not surprising.
 
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