My knotmeter impeller.. - SailNet Community
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post #1 of 19 Old 08-26-2007 Thread Starter
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My knotmeter impeller..

.. grows grass on it everytime I go to use my boat. Makes it stay stuck.

I am getting tired of having that little geyser of water shoot into my boat each time I have to pull it out to clean it.

Is there any product that you can put on the impeller to stop or slow this process down?

thanks,
gh
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post #2 of 19 Old 08-27-2007
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Hi Gh,

Some swear by lanolin to inhibit various underwater growths, but probably the best way is to withdraw it at the END of each session, so you don't have to clean it!

Best,

Matthew (Blue Eagle)
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post #3 of 19 Old 08-27-2007
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The current Raymarine thru-hullhas a clam shell valve that closes when the impeller is withdrwnto minimize the geyser. you might consider replaceing your's next haulout
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post #4 of 19 Old 08-27-2007
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It's not only the impeller itself that will foul with growth and dork up the speed log operation, but growth AROUND the impeller which will alter / block the flow of water. You can have a perfectly cleaned transducer sitting behind a nasty barnacle and your reading will be kittywhampas.

Dive

jef
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post #5 of 19 Old 08-27-2007
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.. grows grass on it everytime I go to use my boat. Makes it stay stuck.
Our problem is weeds. Esp. in the canal in which we're slipped. Usually the problem clears itself after we get out on the lake. Yesterday it did not. We were in light air and really could've used that knotmeter to get additional feedback on sail trim and point-of-sail changes.

I actually considered going below an pulling the damn transducer to clear it, but figured doing that for the first time out in the middle of the lake, whilst The Admiral and I are still learning our way around things, probably wasn't the wisest course of action .

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I am getting tired of having that little geyser of water shoot into my boat each time I have to pull it out to clean it.
Our surveyor told us the mistake most people make is trying to snatch-out the transducer and slap in the plug all in one go. He said the better way to do it is snatch the transducer out, slap your palm over the hole, grab the plug, and quickly put it in place. He told us that, done right, that procedure should result in no more than about a pint or so of water getting in.

I plan to practice at the dock

(ISTM somebody ought to be able to design a knotmeter transducer that wouldn't be susceptible to this "weeds problem." It's rather annoying.)

Jim
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post #6 of 19 Old 08-27-2007
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One old sailor told me that he removes the impellor, then inserts a sponge into the hole. He puts the dummy plug in the hole, pushing the sponge out the bottom, and picks up the sponge when it resurfaces.

I haven't tried this yet, but it sounds like it could work to minimize the water coming into the boat while switching to the dummy plug.

I'd be interested to hear if anyone else has tried this approach, or has other good ideas about minimizing the water flow.

Frank.
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post #7 of 19 Old 08-27-2007
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laying down towels around the transducer helps contain the water.

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post #8 of 19 Old 08-27-2007
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My B&G transducers have screw caps with large thread. It is tied on a string near the transducer. It's not as hard to prevent water coming in when you slap the cap on, but the reverse usually brings in more water... removing the screw cap and getting the transducer back in. That part of the bilge is well contained and so dealing with the water is not too bad.

I use a cooking basting "pump" thingy you get in the super market. It's a squeeze bulb on top of a thick plastic tube. I pump out the water into a plastic container one squeeze at a time and dump it in sink. Great for small spills where a sponge take a long time and a real bilge pump is overkill.

jef
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post #9 of 19 Old 08-27-2007
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SanderO-

Try a microfiber chamois cloth.
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Originally Posted by SanderO View Post
My B&G transducers have screw caps with large thread. It is tied on a string near the transducer. It's not as hard to prevent water coming in when you slap the cap on, but the reverse usually brings in more water... removing the screw cap and getting the transducer back in. That part of the bilge is well contained and so dealing with the water is not too bad.

I use a cooking basting "pump" thingy you get in the super market. It's a squeeze bulb on top of a thick plastic tube. I pump out the water into a plastic container one squeeze at a time and dump it in sink. Great for small spills where a sponge take a long time and a real bilge pump is overkill.

jef
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post #10 of 19 Old 08-27-2007 Thread Starter
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What do you think about coating it with vaseline (petrolium jelly) or something similar?
gh
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