Prop fouled and some expensive near misses

[Olivergm]

After a fun long weekend in Malaysia we pulled into Singapore. 2nm from home we ran over what later turned out to be a big plastic sheet that wound around the starboard prop. The starboard engine (sailing catamaran) ground to a stop. We continued on to the Marina on the port engine while avoiding the harbour traffic. Volvo (saildrive) still went into gear yet revs were limited at 2k. I suspected we had lost the prop. As I got to the Marina I tried reverse on the starboard engine and then forward again and things seemed fine. Unfortunately this testing wasn't enough or the testing just resulted in causing more of an issue. Anyway as I pulled up to my spot the engine revved in gear in reverse but the boat didn't stop or turn. So I couldn't do my usual 180 parking and nearly went crashing into some very expensive boats. Thanks to some good fender work from the Admiral and some good fortune that a mate happened to be leaving his berth on a dinghy that nudged us in.
I have subsequently dived under and pulled out the 3m plastic sheet rapped around the prop. I thought I'd lost the prop but it was still in place. Engine seems to run fine but does not move the prop. Prop spins freely by hand once engines shut down. What do you recon? Gearbox or saildrive shaft? Where to begin?

[Olivergm]

Title should really say near hits. Apologies it's been a long day...

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[delmarrey]

Not knowing the insides of a Volvo sail drive I'd have to take a guess that your clutches got over worked trying to spin that plastic. If you could drain the oil that would tell you, but that would be a haulout, which you might have to do anyway.

[colemj]

If it is a folding prop, it is possible that you spun the hub on it.

Another possibility is that you damaged the damper plate between the saildrive and flywheel - which also contains a rubber hub designed as a fuse to prevent worse damage should the prop jam when the engine is turning it.

As for the clutch, you don't say which model of saildrive it is - assuming it is the 130S, the clutch is a disc pack. It is possible this is damaged, but I would think if so that the prop would still engage somewhat - at least in reverse.

When you shift, can you hear or feel the clutch engage? It should be noticeable even if the prop is not turning.

Mark

[Olivergm]

Hi Mark, yes I believe the clutch did engage. Everything felt as normal aside from the fact the boat didn't slow down, hence I thought I'd lost the prop. Thanks for your input.
The problem here in SG is finding a place to get a cat out of the water...

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[marlinmike]

Not sure on sail drives, but as another posted stated either a spun hub or does that system have a shear pin?

[Olivergm]

Mike, unfortunately no shear pins...Mark, do u know if the rubber hub you referring to is accessible from inside the vessel? I'm loathed to up slip $$$....

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[JPA Cate]

If it's a spun hub, you can remove the prop in the water.....if you're game to get in the water there.

Otherwise, talk to others with similar boats, see if there's a careening beach nearby.

Actually, if you see the vessel "Crystal Blues", a Ganley 53, they're quite knowledgeable folks. Names: Ley, and Neil.

Ann

[Ex-Calif]

Hi Oliver - sorry to hear boat your troubles. Singapore waters are a nightmare of debris. One always has to keep a sharp lookout when motoring.

The back end of the engine has a damper plate bolted on as indicated by Mark. it is there to dampen engine vibes going into the saildrive. Inside the saildrive is the clutch and then the last suspect is the prop attachment itself - I can't see the prop being able to spin or freewheel witout falling off as it is a spline drive.

Unfortunately you are going to need a mechanic and unfortunately to inspect the damper the engine may have to be removed or at least slid forward on its mounts.

Inspection of the saildrive oil and condition by a trained eye could identify clutch issues but its tough to evaluate. Tough way to end a great weekend.

[colemj]

Originally Posted by Ex-Calif

I can't see the prop being able to spin or freewheel witout falling off as it is a spline drive.

Unfortunately you are going to need a mechanic and unfortunately to inspect the damper the engine may have to be removed or at least slid forward on its mounts.

If the prop is a Volvo folding prop, these have rubber hubs like an outboard prop. That hub can be torn and the prop not spin without it falling off. However, if it was torn, I would suspect it would still spin some without force on it, and slip completely with force.

The engine only needs to be disconnected from the saildrive and slide forward a few inches to get access to the damper plate.

Mark

[Olivergm]

Thanks Ex-Calif and Mark, unfortunately they are not folding props just bog standard Volvo two blade props.

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