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post #1 of 7 Old 05-02-2008 Thread Starter
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knot meter paddle thingy

Boat came with Autohelm 4000 / ST-50 system everything works great except the speed indicator and, consequently, the autohelms ability to track on the wind instead of a set heading.

All my local boat advisor's told me about pulling the paddle wheel out from the inside and clearing the debris.

Mine does not seem to come out from the inside.

There is collar threaded over a rubber gasket but there doesn't seem to be any way to get the thing into the boat. It appears to only go out.

The designers of the Nich 31 were paranoid about keeping sea water in the sea. The hatches open aft, the fresh water tank fill from inside the cabin.

What am I missing?

In over my head?
First Boat, a well-equipped 1977 Camper Nicholson 31
What is all this stuff and how does it work?
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post #2 of 7 Old 05-02-2008
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I don't know the 4000 model, on the 3000 it's easy.

Usually, unscrew and release the collar and pull the log wheel sensor out of the mounting tube.

But wait, if the boat is in the water, you need something to put back in the mounting tube to stop the water coming in. There is a dummy sensor provided with the original kit for this purpose. Look for a black cylinder with an identical collar to your log wheel sensor.

Or you could dive over the side and clear the weed of the wheel with a brush.

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post #3 of 7 Old 05-02-2008
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If you have a ST50 knot meter the paddle wheel transducer is made to be removed for cleaning purposes. There is also a dummy transducer that you put in as a plug while you have the other transducer out. The top portion of the transducers have locking collars that screw the transducer tightly in place. In order to remove the transducer you must unscew the collar. Then you can pull the transducer. Some - not alot - of water will come in before you can get the dummy transducer in place. Clean the paddle wheel and then reverse the procedure. You must have that dummy transducer or you will get alot of water.
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post #4 of 7 Old 05-02-2008
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The VDO speed log sender unit (transducer) on my last boat is most likely much different than your Autohelm, but I believe the design principle is similar to most units.

Please excuse this low quality pic, taken just after purchase and before clean up. It shows the dummy plug in place and the sender unit with paddle wheel on the stringer to it's lower left. Both simply screw into the threaded sleeve of the through-hull.

True Blue . . .
sold the Nauticat
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post #5 of 7 Old 05-02-2008
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On my boat there is a pin secured by a ring clip which must be removed before the speen indicator can be pulled from it's housing. After removing this pin I was able to remove the unit and quickly insert a wooden plug in it's place. It was a bit scary, but all went well. You might want to have someone there who has done this before. Good luck with yours.
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post #6 of 7 Old 05-02-2008
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Seems like you have to unscrew the collar, hold the ring, and give a quarter turn counterclockwise, then pull. Probably hard to get out if it has been in there a while..

There should be a rubber gasket that closes to reduce the water intake. Stick the plug or any plug in there if your boat did not come with one.

I use bilge cleaner and a tooth brush (usually my mother in laws) to clean the crap off of there. Depending on how long it has been, you will need an ice pick or screw driver to get off the freaking barnacle farms. Some people at the dock have told me to use muratic acis or soak in Cl but I have not had the heart to try that yet. I know muratic acid takes them off, just concerned about its effect on the wheel, etc. Why don't you try it and let me know?(smile).

Hope that helps.

- CD
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post #7 of 7 Old 05-03-2008
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I just go over the side and scrub it with a toth brush. Its faster and than there is no problem with water coming in.

If the paddle wheal is damaged you can get a replacement.

Sea Fever
Bristol 29.9 #49
Southern Maine
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