Volvo Penta MD7A / 110S Sail Drive Clunking Issue

[scw]

Hi there,

I am looking for some advice on an issue that has just started to happen with my Volvo Penta MD7A / 110S Sail Drive.

I’ve been regularly starting and running the engine over the winter and getting the boat ready for the summer season, and a few weeks ago I noticed a clunking sound that was coming up from, I think, the sail drive leg.

The clunking appears to only happen in forward gear; I have not yet been able to replicate it in reverse. The last time I ran it, I had it in forward gear for about 4 minutes before the clunking started happening, whereas previously it'd happened within a minute of being in gear. I thought maybe the prop or roper cutter had come loose, or maybe something was wrapped around the prop. In order to rule a few things out, I went under the boat to look (she sits in mud at low tide). Other than it looking dirty and needing a coat of paint and maybe a new anode, everything looks ok, or so I believe. I’m no expert with boats or engines, so please correct me if you see anything alarming in the attached photos or videos. When in gear, the boat does move forward, so the prop is turning okay, although it might be losing a bit of power. It's hard to tell as it’s only a 13-HP engine and tidal, so getting a true gauge is difficult. The sail drive oil is at the correct level and looks very clean. Engine oil is also at the right level and looks ok.

Here are the videos that show the engine running and the prop movement.

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I am at a bit of a loss for how to find the cause so that I can fix the issue. If she needs to come out of the water, I would ideally like to know what I am looking to fix or order beforehand. Any help would be much appreciated.

Many thanks for looking.

 

[Tranona]

The bearings in the cutter need replacing - you can see the wear grooves on the face of the blade.

Instructions here ropestripper.com/documents/servicing-amsd.pdf

 

[scw]

The bearings in the cutter need replacing - you can see the wear grooves on the face of the blade.

Instructions here ropestripper.com/documents/servicing-amsd.pdf

Thank you Tranona, I appreciate your help and link. I will look at getting that fixed. I just realized my videos were not visible but they are now.

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[kwb78]

There is a rubber damper that couples the output of the crankshaft to the input of the saildrive. It looks like this:



You can see the three drive pins on the back of the crank, and the saildrive also has three which fit in the empty slots. If the damper is knackered you might be hearing contact between the pins. It happening while in gear would fit because there will be more load on it compared to when idling in neutral which will tend to squash the rubber. If you have a long screwdriver or metal rod you might be able to localise the sound a bit better by holding one end to your ear and the other to different places on the casing.

 

[Tranona]

Now having heard the videos agree the knock is probably the damper plate and the scraping sound from the prop the worn (or probably non existent) bearings in the cutter.

 

[scw]

There is a rubber damper that couples the output of the crankshaft to the input of the saildrive. It looks like this:

View attachment 177701

You can see the three drive pins on the back of the crank, and the saildrive also has three which fit in the empty slots. If the damper is knackered you might be hearing contact between the pins. It happening while in gear would fit because there will be more load on it compared to when idling in neutral which will tend to squash the rubber. If you have a long screwdriver or metal rod you might be able to localise the sound a bit better by holding one end to your ear and the other to different places on the casing.

That's really helpful; thank you for that. Unfortunately, I am not someone who has a great knowledge of engines and sail drive mechanics, so this may be a very silly question. If I opened up the top section of the sail drive, would that help me confirm your diagnosis? When I bought the boat, the engine didn't work, and with some great YouTube videos, I managed to take things apart and resolve the issues. I'd like to tackle this one but need to workout to see if I can get to the problem areas or if it's something I need the boat out of the water for and a professional mechanic. Thanks again for your input. I will do a bit of Googling on the crankshaft now.

 

[scw]

Now having heard the videos agree the knock is probably the damper plate and the scraping sound from the prop the worn (or probably non existent) bearings in the cutter.

Thanks for that, all very helpful information. Do you think it would be possible to replace the bearings in the cutter whilst it's in the mud? I know this isn't an ideal location to carryout any work, but getting the boat out the water now may be a challenge. Thanks again.

 

[Tranona]

Yes, if you can remove the propeller. The cutter then slides off. 10 minute job to take it apart with allen keys, replace the bearings and reassemble. The kit comes with new screws. Your anode looks OK but does not seem to be doing much - is it in fresh or brackish water?

 

[kwb78]

If I opened up the top section of the sail drive, would that help me confirm your diagnosis?

No you can't get access to the damper from the top cover. If you open the top plate, you will see the input bevel gear, cone clutches and selector and the top of the counter shaft. You actually have to separate the drive from the back of the engine. The sail drive and engine are mutually supporting, in that the engine has two mounts at the front, and the sail drive has a single one at the rear. To separate them, you need to support the back of the engine and the front of the sail drive, then undo these bolts on both sides:



If you have access to the front of the engine, you may be able to slide some wood under the sump for it to sit on and depending on your engine bay you might be able to slide it forwards on a plank. It's a bit of a heavy lump though, so you need to be a bit careful. If you don't have space to support the front of the sail drive, you might need to bring the boat ashore and support it from below. Once unbolted the engine and sail drive just come apart - there's no shared oil system or anything like that to make a mess.

It's quite a lot of work just to confirm that as a diagnosis, so you might want to get someone knowledgeable to take a look before you commit to it.

 

[scw]

Yes, if you can remove the propeller. The cutter then slides off. 10 minute job to take it apart with allen keys, replace the bearings and reassemble. The kit comes with new screws. Your anode looks OK but does not seem to be doing much - is it in fresh or

Yes, if you can remove the propeller. The cutter then slides off. 10 minute job to take it apart with allen keys, replace the bearings and reassemble. The kit comes with new screws. Your anode looks OK but does not seem to be doing much - is it in fresh or brackish water?

That's good to know. Thanks. I'm based in Rye Harbour, but the prop is nearly always in the mud which may help protect the anode, it was replaced just under two years ago.

No you can't get access to the damper from the top cover. If you open the top plate, you will see the input bevel gear, cone clutches and selector and the top of the counter shaft. You actually have to separate the drive from the back of the engine. The sail drive and engine are mutually supporting, in that the engine has two mounts at the front, and the sail drive has a single one at the rear. To separate them, you need to support the back of the engine and the front of the sail drive, then undo these bolts on both sides:

View attachment 177725

If you have access to the front of the engine, you may be able to slide some wood under the sump for it to sit on and depending on your engine bay you might be able to slide it forwards on a plank. It's a bit of a heavy lump though, so you need to be a bit careful. If you don't have space to support the front of the sail drive, you might need to bring the boat ashore and support it from below. Once unbolted the engine and sail drive just come apart - there's no shared oil system or anything like that to make a mess.

It's quite a lot of work just to confirm that as a diagnosis, so you might want to get someone knowledgeable to take a look before you commit to it.

Thank you, that's a great help. I'm getting a much better understanding of all the mechanics from all the input on here. I will take a look at the access and see if this is viable while in the water. Would the bolts around the circular seal need undoing as well? I assume that the circular seal is what is stopping sea water from getting into the boat and sinking it?! I plan on replacing that seal and cleaning / painting the engine next winter.

 

[kwb78]

Those bolts secure the ring which holds the seal in place, so definitely don't undo them while in the water.

You can see what the input of the sail drive looks like in this video: