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Catalina/Capri 25/250 Sailor's Forums

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Knot Meter Cleaning

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cat1951
Admiral

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USA
636 Posts

Initially Posted - 08/07/2008 : 09:06:12

My knotmeter has stopped recording our speed and I am pretty sure it is due to the paddle wheel becoming clogged with algae and such. I am planning to get under the boat and clean it, but want to make sure I don't do something to damage the wheel.

Do any of you have any suggestions, or is it just a matter of cleaining it with something like a car wash glove.. you know, the one that looks like a floor mop in the shape of a glove.

Mike
Grand Lake, OK
N.O. Catalina 25 #4849
In my opinion 75% of the earth is water for a reason. That's why I sail.

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 08/07/2008 : 09:54:44

It's not particularly fragile... But if you can reach it with a hose and nozzle, that might do the best job.

Edited by - Dave Bristle on 08/07/2008 09:55:57

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 08/07/2008 : 09:57:26

I clean my paddlewheel from the inside of the boat.

Edited by - on

tinob
Master Marine Consultant

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USA
1883 Posts

Response Posted - 08/07/2008 : 11:29:43

] do as Don does.

And to accomplish this you need to pull the speedo mechanism from the boat and plug the hole with the plug that comes with the speedo sending unit, or something that will accomplish the same thing, namely keeping the water out until you've had an opportunity to clean the wheel. I use a tooth brush to clean the wheel segments. Sometimes it is necessary to remove the wheel to do the job right. There is a pin on the side of the sending unit that needs be pushed out to release the wheel. Having done this you have the opportunity to clean the recesses into which the wheel rests. I've found barnacles in there and a bevy of eel spawn once, all of which minimises the accuracy of the speedo, (GO GPS). Once done cleaning the wheel there is just the replacing of it. Be aware that the wheel can be put in backwards...the cup end of the wheel segments must face forward. OR ELSE !!!
Driving through sheet ice will shear off the wheel segments necessitating replacement of the wheel. If driving through ice remove the speedo unit and replace with the plug that comes with the unit.
Val on Calista, #3936, Patchogue, N.Y.

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cat1951
Admiral

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USA
636 Posts

Response Posted - 08/07/2008 : 12:49:59

OK.. this is probably a stupid question, but here goes. Won't the boat fill with water if you remove the sending unit from the inside. I have visions from the movies that I have seen where the water is rushing in and sailors are trying to plug the hole. Also, not sure where the plugs are since we bought the boat used. I will ask the P.O.

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dmpilc
Master Marine Consultant

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USA
4593 Posts

Response Posted - 08/07/2008 : 12:57:05

My guess is that you have to make the plug swap-out VERY quickly to minimize the amount of water coming into the boat. The inside of the boat will get wet; speed will determine just how much.

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cat1951
Admiral

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USA
636 Posts

Response Posted - 08/07/2008 : 13:54:48

Thanks David, the P.O. said that there are small flaps that close the opening when/if one pulls out the unit, and yes there will be some that enters the bilge. However, he also indicated that the paddle wheel is easily within arms reach by just being in the water next to the hull. Since the temp has been around 100+ lately, and expected to be in the 90's this weekend, I think a swim is just what is called for.

Edited by - cat1951 on 08/07/2008 13:55:42

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 08/07/2008 : 14:24:37

Even if you casually remove the paddlewheel transducer and put in the plug, not much water comes inside the boat. When I did it the first time, I pictured water shooting in, but it was rather a non-event with maybe just a cup of water dribbling in.

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cat1951
Admiral

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USA
636 Posts

Response Posted - 08/07/2008 : 15:17:44

Thanks Don, I will remember that for future cleanings where the water temp is not what it is now.

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Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 08/07/2008 : 15:19:21

When you pull the wheel it doesn't leave the whole hole open. There are little "doors" that seal most of the hole.

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tinob
Master Marine Consultant

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USA
1883 Posts

Response Posted - 08/07/2008 : 15:52:15

When I pull the odometer from its position on my boat water rushes in, there are no little flaps of doors to control the influx of water . The technique that works for me is to have the plug handy, pull the sending unit and immediately cover the opening with your free hand, then bring the plug alongside the opening and let go your hand and replace it with the plug. It's a little intimidating at first, just don't panic. Of course the procedure has to be repeated after you've cleaned the wheel and its resting place. When replacing the sending unit be sure to have the arrow facing forward.

Val on Calista, #3936, Patchogue, N.Y.

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ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 08/07/2008 : 19:15:30

I've found the only way to reliably clean the knotmeter is to pull it inside. It doesn't take much 'crud' to make it read low or stop spinning altogether.

I will say that it is a bit unnerving to see a hole appear in the bottom of the boat for a moment... but I usually don't get more than a pint or two of water in the boat while swapping.

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John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 08/07/2008 : 19:21:51

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Nautiduck
 When you pull the wheel it doesn't leave the whole hole open. There are little "doors" that seal most of the hole.
<hr height="1" noshade id="quote"></blockquote id="quote">That wasn't the case when I pulled mine. I made the switch quickly and didn't get any more water than a beach towel could handle easily.

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Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 08/07/2008 : 23:56:57

Interesting. My Raymarine ST60 Speedo has "flap valves" that flip down when you remove the speed wheel setup. That stops almost all water while you insert the plug. Handy feature.

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