Fouled Twin Volvo Penta 27 HP Saildrives

[meduf]

Hello everyone! I am not new to sailing, but new to catamarans and sailing on the ocean, We bought this Leopard 40 from Moorings a month ago and have been making sure she is recognizable as ours by the few scratches we have put on her, but nothing major. We even fouled both Volvo Penta 27 HP Saildrive Props with 2 mooring lines. Now neither of us thought anything about the fouling until the local SeaTow guy asked us if we had replaced the props the next day. Then yesterday we were moving from the fuel dock over over dock, he said, "I was watching you try to move and I think you were slipping. You haven't replaced those props yet have you?"
His position is as follows: Due to the power from these twin Volvo Penta 27 HP Diesels, that they will rip the motors off the motor mounts unless they have a sacrficial prop. This prop then must be replaced as it no longer has the ability to move water properly due to the stress the fouling applied.
Is this a true statement? Should the props be replaced after fouling? Is there anyway to test the props or should they just be replaced regardless? Is there anyway to replace them without having to have the vessel hauled out?
Thank you very much for your opinions. I am in St Croix and have already been paying the marina a small fortune to fix a few other things. Given the size of this issue, I wanted to get some thoughts from others not close by.

[belizesailor]

Rubbish.

Maybe your SeaTow guy has a buddy in the prop biz.

If you have the original fixed blade props installed on your sail drives then they do not have a sacrificial hub (this is common for example on small outboard engines, but not on marine diesels) -- on Volvo sail-drives the hub of the prop mates directly to the prop shaft grooves -- nothing sacrificial here -- the standard fixed blade prop is one solid piece of metal. Yes, you can damage your drive/engine by heavily loading a fouled line. You could also damage the prop. If you are concerned that you might have done this then pull the props and get them to a good prop shop -- they can check them out for you and correct small problems if necessary. Dive them and see if there is any obvious damage first.

Another common problem when fouling sail drives is damage to the shaft and/or shaft seals. A bit of heavy monofilament wrapped up tightly around the shaft can damage both. Check the oil in your gear box after running in gear for a few minutes -- if it is milky-white in color the your seals are leaking. This can be caused by damaged seals and/or shaft.

The sail drives themselves are quite tough (complicated, but tough). It is unusual to do internal damage unless you really tweaked them hard. If shifting feels different then this could be the case. Probably not, but it can be done. Hope not, because sail drive repairs are crazy expensive.

[LeaseOnLife]

The guy is full of sh*t

Here is the Prop-Catalog from Volvo:

http://www.volvopenta.com/SiteCollec...er%20Guide.pdf

From page 18 you find the Volvo folding props for saildrives, from page 21 you can see the non folding props.

Identify your prop from the catalog and you will see it doesn't have anything to slip.

Check the oil of the transmissions, not just for water, but if something is/was slipping (cone or clutch) you might be able to smell it.

We fouled our prop (not a saildrive) twice. The engine kept running, the clutch in the transmission slipped, and because of the load of the blocked prop we couldn't switch to neutral, we had to stop the engine. We changed oil after each event.

[Ram]

Originally Posted by belizesailor

Rubbish.

Maybe your SeaTow guy has a buddy in the prop biz.

If you have the original fixed blade props installed on your sail drives then they do not have a sacrificial hub (this is common for example on small outboard engines, but not on marine diesels) --.

I have the original fixed props and ( I beleave) they have the sacrificial hubs -- yammer sail drive is different from yours perhaps

[colemj]

The Volvo saildrive folding props do have a rubber hub that can be damaged. However, if your prop was "slipping" because of damaged hubs, it would be immediately noticeable by you even if you had no idea what to notice. The engine would rev up and you wouldn't be going anywhere.

Mark

[Ram]

Originally Posted by colemj

The Volvo saildrive folding props do have a rubber hub that can be damaged. However, if your prop was "slipping" because of damaged hubs, it would be immediately noticeable by you even if you had no idea what to notice. The engine would rev up and you wouldn't be going anywhere.

Mark

Mark I had damaged one of mine and it took me a few weeks to figure what was wrong- mine worked but there was a small vibration that I was the only one who could notice it, finally I pulled the prop and it had slipped out about 1/4 inch

[belizesailor]

Originally Posted by Ram

I have the original fixed props and ( I beleave) they have the sacrificial hubs -- yammer sail drive is different from yours perhaps

Yes, the Yanmars are different in a few ways. I have Volvo sail drives with the original fixed props and there is definitely no sacrificial hub -- have not seen them on other Volvo's either. Of course, there might be exceptions, but I have not seen them (and OP did not state whether fixed or folding).

[belizesailor]

Originally Posted by colemj

The Volvo saildrive folding props do have a rubber hub that can be damaged. However, if your prop was "slipping" because of damaged hubs, it would be immediately noticeable by you even if you had no idea what to notice. The engine would rev up and you wouldn't be going anywhere.

Mark

Good point, if OP does have sacrificial hubs then failure is very noticeable even if you are inexperienced. I spun the hub on my skiff's prop recently...manged to coax it to do do about 3 knots all the way back home...long ride.

[marshmat]

If a rubber hub is shot, you'll notice. Everything will be fine up to 1/4 throttle or so, then the hub will let go and the engine will rev easily without providing any thrust. It'll re-engage if you pull back to idle. Every rubber-hub prop I've encountered could be replaced in the water, no haul-out necessary, although you might need breathing apparatus to reach it.

It is possible to bend the blades of a small propeller if you wrap a mooring line around it. If this had happened, you'd still have thrust at all speeds, but there would not be as much thrust as usual, and there would probably be excess vibration. Bent blades are easily diagnosed by swimming under the boat and looking at the prop (with all engine start/run interlocks locked out, of course).

If the mooring line stopped the prop but the engine didn't stall, the clutches may have slipped. (This is only possible with cone clutches, which rely on friction between two mating surfaces. If you have dog clutches, something must break, stall or pop loose instead, since there's nothing to slip.) The gear oil would reveal this- it would smell like, well, burned clutch and might be blacker than normal. Flushing and changing the gear oil would be a very good idea if this is the case. (If the oil looks milky, you have water ingress- likely a damaged shaft seal- which does call for a haul-out.)

It's also quite possible that nothing was damaged, and the drives and props are fine. If the prop looks OK and works OK, and the gear oil is good, the odds are that everything's actually OK.

[Cheechako]

Originally Posted by belizesailor

Good point, if OP does have sacrificial hubs then failure is very noticeable even if you are inexperienced. I spun the hub on my skiff's prop recently...manged to coax it to do do about 3 knots all the way back home...long ride.

On small outboards I have not found that a spun hub will necessarily be real noticeable. Depends on how badly damaged. Goose it hard and you notice the differnce. ease up to a plane and hard to notice. Maybe the OP should go out and gun the motor rather than ease up and see what it does....?