Kelp causing engine vibrations?

[Letterkenny]

Went out sailing today in San Diego and was having a good time. There was quite a big swell coming through but it is a very long period and deep waters so there were a lot of boats out there. A big ground swell always picks up a bunch of junk in the water and tears the kelp beds. I do my best to avoid them but it’s inevitable that you will hit some especially with twin rudders.

After some good sailing out, we turned around to head in and snagged some kelp which really killed our speed from 6.5-7 knots to 3.5 knots. We were trailing a good amount from the rudders which we get some off with a boat hook or going on the swing platform and pulling off/with a knife but we must have something in the keel. Normally we back down in reverse to try to get this off but due to the swell, we waited until we were within the harbor. We didn’t get much off from backing down but did see some bits and pieces being cut up by the prop when going back forward. However, we eventually got a lot of vibration and couldn’t do more than 2.5-3 knots at 2600rpm that normally had us at 6 knots. Would the kelp cause this or other fouling? After a bit we stopped again to try to clear more off and this seemed to stop the bad vibration but I didn’t see anything come off from around there. Just want to make sure I don’t have more of an issue here. I would dive it but it’s cold this time of year so just asked my diver to see if he can come earlier.

[SailingHarmonie]

If kelp gets wrapped around your running gear, yes, of course it will cause vibration, maybe mild, maybe severe depending on the amount wrapped up, and the specifics of how.

You have a boat custom made to have this kind of problem. From the twin rudders to the keel shape, it seems designed specifically to snag the maximum amount of debris possible.

Before you hire a diver, you might consider tying a waterproof camera on the end of a boat hook and poke it overboard to have a look-see.

[Letterkenny]

Originally Posted by SailingHarmonie

If kelp gets wrapped around your running gear, yes, of course it will cause vibration, maybe mild, maybe severe depending on the amount wrapped up, and the specifics of how.

You have a boat custom made to have this kind of problem. From the twin rudders to the keel shape, it seems designed specifically to snag the maximum amount of debris possible.

Before you hire a diver, you might consider tying a waterproof camera on the end of a boat hook and poke it overboard to have a look-see.

Very true, she likes to grab a lot of crap. I was going to use my GoPro to see but not enough light by the time I was able to get in and didn’t have any of my dive lights. My diver comes monthly anyways to clean the bottom so was just going to move it up (might be on schedule actually) since I have guests wanting to go out in early January.

I was just surprised with the amount of vibrations and would have thought that the prop would have chewed the kelp up quicker to get rid anything on it causing the vibrations.

[donradcliffe]

You never know. I've had bullwhip kelp completely stall the engine on a 40 footer. I've also had discarded nets ball around the prop. I also had similar symptoms off Dana Point turn out to be a contractor's heavy trash bag on the prop. Coming out of the Suez Canal it was a fiberglass cement bag. Then there are the crab and lobster pots.

I would alternate forward and reverse at up to 80% throttle and see if things improve. A camera would definitely help.

[SailingHarmonie]

Originally Posted by Letterkenny

I was just surprised with the amount of vibrations and would have thought that the prop would have chewed the kelp up quicker to get rid anything on it causing the vibrations.

It is sometimes surprising how inefficient a "chopper" a propeller can be. Especially if you have a long-ish shaft exposed that kelp stems can wrap around and not even get into the prop. A good sharp line cutter on the shaft can really help, although nothing I have found is a 100% sure fire solution.

I have known boats to get even stem-les sargassum weed so balled up around the prop that the boat stopped.

[Letterkenny]

Originally Posted by donradcliffe

You never know. I've had bullwhip kelp completely stall the engine on a 40 footer. I've also had discarded nets ball around the prop. I also had similar symptoms off Dana Point turn out to be a contractor's heavy trash bag on the prop. Coming out of the Suez Canal it was a fiberglass cement bag. Then there are the crab and lobster pots.

I would alternate forward and reverse at up to 80% throttle and see if things improve. A camera would definitely help.

I had a bathroom rug on one of my rudders once after coming in wrapped in kelp so that all makes sense.

Originally Posted by SailingHarmonie

It is sometimes surprising how inefficient a "chopper" a propeller can be. Especially if you have a long-ish shaft exposed that kelp stems can wrap around and not even get into the prop. A good sharp line cutter on the shaft can really help, although nothing I have found is a 100% sure fire solution.

I have known boats to get even stem-les sargassum weed so balled up around the prop that the boat stopped.

Might look into a line cutter. Some other folks that have the same boat as I do added some fiberglass knives essentially in front of the two rudders. Curious how those work out. At least with the rudders it is easier to get on the swim platform and pull it off. I think I saw somewhere on here what is essentially a boat hook but the hook is a large u shaped knife. Could be something else to try but that wouldn’t solve the issue I had today as it seemed to be farther up by the keel or shaft. I did try to use a boat hook and see if I could catch anything back at the dock from the front of the keel but unfortunately I couldn’t reach or catch anything at full extension.

[wholybee]

I have snagged Kelp, fishing lines, and fishing nets.

I carry a wetsuit when sailing in cold water. Being disabled because of a fouled prop could be dangerous, and motoring with the intense vibrations could damage something. When I was off San Diego and was fouled by kelp, I jumped in really quick without my suit just to see how bad it was. I was in the water only about 20 seconds, and that was enough to clear it.