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MikeinLA 09-30-2006 03:24 AM

Stuck Knotmeter Paddle Wheel
Hi all. Is there any way to unstick a severely stuck knotmeter paddle wheel? It hasn't been cleaned in years and will turn by hand, but slowly. Certainly does not spin freely. Any ideas? It's a Raymarine Tridata transducer if that helps. Failing that, can you buy just the transducer?



Sasha_V 09-30-2006 03:37 AM

Yes you can, in fact you can buy just the replacement paddle wheel and the bushes it spins in. Which sounds like it ought to be a cure for what ails you.

Just make sure that you test to see if the rest of the system works by having someone stay up top to watch the display and someone down below spinning the wheel for a would be annoying to swap out the bits only to find that the rest of the system is also clapped out.


Rockter 09-30-2006 07:10 AM

The one for my Datamarine system is getting noisy, but still works. I hope I can find another one when it becomes intolerable.

FrankLanger 09-30-2006 01:38 PM

If the system works, but has become fouled with "sea critters" and algae, can the impellor be cleaned properly to restore it's function? If so, how is this best done, and with what cleaners/tools?

capttb 09-30-2006 01:58 PM

Yes, and in our waters needs to be done often. You should have a "blanking plug" hopefully wired to the transducer, it's to put in place of the 'ducer to stop water coming in while you clean. Most Raymarine's have a flapper valve that reduces the flow when you pull the transducer and there's little pressure so you don't get too much water before you get the blanking plug screwed on. Then you need a paper clip to push out the axle pin on transducer paddlewheel. Paddle may be cleaned with fine wire brush if metal, Plastic parts can be scraped with butter knife etc. carefully. We mostly get some kind of worm that leaves a white "casing" everywhere that fouls the paddle. I've attached link here to the manual for the ST50 speed,an older model, the Ray website has the manuals available online for most instruments.

sailingdog 09-30-2006 04:09 PM

IIRC, the paddle wheel just spins in the bushings, and isn't physically connected to the electronics (believe they use either Hall effect or magnetic sensor) via gearing of any replacing the paddle is pretty easy. In many cases, you can remove the pin and then clean the paddle and the housing, and then replace the original paddle.

MikeinLA 09-30-2006 04:35 PM

Thanks for all the good ideas. Lots of things to try. Boy don't you just love pulling that transducer? I don't have a flapper like the newer models and it really gives you that "my boat is sinking" feeling for a split second. Very exciting.


FrankLanger 09-30-2006 05:53 PM

I've only replaced the transducer with the "dummy" plug once--worked o.k., but I'm concerned about losing the "O" ring that seals it, due to the water rushing in for a second or two. Any tips to avoid that, or guidance on the proper way to do this quick but important maintenance task?

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