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Old 22-01-2021, 18:13   #1
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Fouled Prop: Potential Transmission/ shaft Damage.

I stupidly fouled my prop today with my long bow line. We were motoring at about 2700 rpm, when the prop got stuck by the bow line. The engine immediately stopped (Of course, it happened in very rough conditions)

I have a diver coming next Monday to get the line off the prop.

My questions:

1. I can not get the gear shift out of forward. Is there a way to do this once the prop is free of the line?

2. My PYI PSS Dripless shaft seal compressed when this happened (See Photo). I can not get my head around why this happened when the shaft suddenly stopped spinning. Any ideas on why this particular thing happened?

3. The engine just stopped suddenly. There were no grinding noises from the transmission. Should I expect major transmission problems?

Thanks.
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Old 22-01-2021, 18:28   #2
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Might have damaged transmission, try changing fluid anyway it won’t hurt and look for any problems in drained fluid. Good luck
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Old 22-01-2021, 18:28   #3
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Looks like the rope has caused the shaft/tranny/engine in some degree or another to pull to the aft a few inches. When the rope is removed I would make sure the shaft is still seated properly in the coupler then fire it up dockside and check for any imbalances/vibration. Depends on the transmission really mechanical or hydraulic. I wouldnít be too worried but I would get the tension of ASAP and keep an eye out for leaks or sounds once itís back up and running. The other thing to consider is your damper plate and how much it absorbed or was damaged. If it wonít spin it doesnít necessarily mean your tranny is shot might just be a busted plate but you will be removing the tranny if thatís the case.
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Old 22-01-2021, 18:43   #4
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Quote:
Originally Posted by rbk View Post
Looks like the rope has caused the shaft/tranny/engine in some degree or another to pull to the aft a few inches. When the rope is removed I would make sure the shaft is still seated properly in the coupler...
What he said. The rope got wedged between the prop and the strut or hull and pulled the shaft aft. The PSS collar stayed where it was on the shaft, so compressed the bellow. My guess is you will find a line on your shaft about 2-3" inches aft of the coupler that will show you where it used to sit in the coupler. That or it pulled the whole engine aft
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Old 22-01-2021, 20:44   #5
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Thank you for the replies.

You are correct. I went back to the boat and checked. The fouled line pulled the engine forward. That is why the dripless shaft is compressed.

The engine mounts are bent about an 1" aft.

What a mess.

I guess at a minimum I'll need all new engine mounts (Yanmar 3GM30f). And, then who knows what further damage is there.
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Old 22-01-2021, 21:02   #6
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

The fact that itís stuck in gear might be a good thing, your damper plate and transmission might be ok. If it was free spinning not so much.
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Old 23-01-2021, 02:16   #7
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

had a similar issue few years ago when we picked up a large clump of rope on one sail drive.

fortunately not going fast at the time (4-5k / 1500rpm), but it still broke one of the engine mounts (Yanmar 4JH2TE). despite this we managed to motor 100' or so to reach port

fortunately no damage to saildrive, gearbox or prop

hope yours turns out ok (lifting the engine to replace engine mount is not too hard - esp on a little 3GM )

cheers,
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Old 23-01-2021, 10:05   #8
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Had Similar accident

Line attached to forward Sampson posts
Fouled shaft
Stopped idling engine abruptly
After removal and running engine, transmission
grinding noise

all the bearings in transmission destroyed
hardened gears AOK
Yamaha transmission rebuilt
$$$
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Old 23-01-2021, 11:44   #9
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Quote:
Originally Posted by FuneSF View Post
I stupidly fouled my prop today with my long bow line. We were motoring at about 2700 rpm, when the prop got stuck by the bow line. The engine immediately stopped (Of course, it happened in very rough conditions)

I have a diver coming next Monday to get the line off the prop.

My questions:

1. I can not get the gear shift out of forward. Is there a way to do this once the prop is free of the line?

2. My PYI PSS Dripless shaft seal compressed when this happened (See Photo). I can not get my head around why this happened when the shaft suddenly stopped spinning. Any ideas on why this particular thing happened?

3. The engine just stopped suddenly. There were no grinding noises from the transmission. Should I expect major transmission problems?

Thanks.
I'll bet you splice your bow lines shorter in the future.
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Old 23-01-2021, 14:45   #10
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Assuming you have one you may also want to check the shaft movement in the cutless bearing. More than 1mm will generate an elliptical spin and it will feel as if the engine is about to knock a hole in the hull. Not easy to inspect under the water though.
In addition, and it may not have stopped the prop wrap, but do you have a rope cutter fitted? If not I personally would recommend getting one.
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Old 23-01-2021, 14:56   #11
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

It is quite possible that the prop/strut/shaft (any or all) are bent, especially considering the damage to the engine mounts. I think you should consider a haulout to remove and inspect them.

Greg
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Old 23-01-2021, 17:45   #12
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Thank you all for your comments.

I spent the day at the boat working on this issue with an an engine expert that lives at the marina. We were able to get the line off the prop. The engine mostly moved back into place. But, the mounts are shot and I will replace those asap.

We got the transmission to shift into neutral and ran the engine under load in forward and reverse. The engine is vibrating more than usual due to the mounts. But, I thought it would be a lot worse. Amazingly, the transmission seemed fine and shaft/ prop were spinning normally. If I escape this with only needing to change the engine mounts, I will be very happy. I'm going to take the boat out on a calm day next week and run her at various rpms in forward and reverse. If transmission/ shaft/ prop issues arise, I will get the boat hauled out and everything properly checked.

Please see photos of the forward mounts before the line was taken off the prop. You could see how stretched they were and that one is completely shot.
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Old 23-01-2021, 18:05   #13
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Quote:
Originally Posted by FuneSF View Post
...



I guess at a minimum I'll need all new engine mounts (Yanmar 3GM30f). And, then who knows what further damage is there.

I would absolutely replace the bellows on the shaft seal. That compression was way outside their specification, plus they were left compressed like that for a considerable period of time. (Unavoidable, I know.)

Iíve read a lot about these dripless seals (having the same on my boat) and the big takeaways for me were that they fail in a very nasty way when they fail and that the most common modes of failure are the disk slipping on the shaft, closely followed by the rubber bellows tearing.

For what is is worth, I keep a shaft anode clamped to the shaft in front of the disk as a backup to the grub screws.
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Old 23-01-2021, 19:18   #14
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Thank you. I will get the bellows replaced the next haul out, which will likely be soon.

That is a very good idea about the zinc anode on the engine side of the shaft seal.
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Old 23-01-2021, 19:29   #15
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Re: Fouled Prop: Potential Transmission/ shaft Damage.

Quote:
Originally Posted by FuneSF View Post
Thank you for the replies.

You are correct. I went back to the boat and checked. The fouled line pulled the engine forward. That is why the dripless shaft is compressed.

The engine mounts are bent about an 1" aft.

What a mess.

I guess at a minimum I'll need all new engine mounts (Yanmar 3GM30f). And, then who knows what further damage is there.
Yes I was going to say check the mounts. No way the engine could move that far without damaging them. Hopefully that's all it did, but I'd expect the shaft to be bent too. Mine did that and I was only turning about 1600 when it fouled. 3/4" shaft on that one.
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