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pkeyser's picture
pkeyser
Last seen: 5 hours 13 min ago
Joined: 5/18/13
Posts: 241
Knot meter wheel

Does anybody have a suggestion on how to keep the knot meter wheel free from fouling? My speed sensor wheel seems to pick up small amounts of seaweed or floatsum which stops if from spinning and registering speed. It's fine at the start of the season, but by this time of the year, I have to clean it frequently to free it up. 

I have a Raymarine unit. Our previous boat had a Data Marine unit. After 15 years, it too became very sensative to small amounts of seaweed. Data Marine suggested I replace the wheel and pin. They claimed it only took a tiny bit of wear to stop the unit from measuring the correct speed; the pickup gap would grow too large to generate a signal from the wheel. Sure enough, the new wheel worked great and addressed the issue. Can the Raymarine wheels be replaced? I couldn't find any info on their site.

Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

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Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

rjwilson's picture
rjwilson
Last seen: 1 hour 13 min ago
Joined: 4/28/14
Posts: 29

I started a couple of years ago using bottom paint on the knot meter wheel and the cavity on the sensor. It has worked wonder in the warm waters of the lower Chesapeake Bay. Now I only take the sensor out once during the season for a cleaning.
 
Yes the wheel can be replaced. What Raymarine (and the other manufacturers) don’t like to tell you I that they don’t make the sensors. They are made by another company and for the speed and depth sensors most get them from a company named AIRMAR Technology Corporation in Milford, NH. My guess is your knot meter replacement wheel would be a Airmar 33-113 Paddlewheel Kit. They are running in the $20-25 range depending on where you buy it.
 

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Bob Wilson
S/V Morning Breeze
2003 Catalina 36, Hull 2122
Williamsburg, VA
pkeyser's picture
pkeyser
Last seen: 5 hours 13 min ago
Joined: 5/18/13
Posts: 241

Thanks very much Bob!

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Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

LeslieTroyer's picture
LeslieTroyer
Last seen: 21 hours 41 min ago
Joined: 3/13/16
Posts: 261

They make anti-foul paint specific for the speed sensor,  don't remember brand right now but comes in small bottle with a brush on the lid.

 You can remove and clean the sensor while in the water. It is exciting the first time but I've got it down to less than a pint. Make sure the blanking plug is handy,  unscrew the plastic retaining nut then pull the sensor with your right hand and cover hole with left palm. Pick up the plug with right hand and quickly insert into the hole.   Some racers in Florida pull them when finished for the day and install at the beginning.  The new sensors have a trap door in the thruhull fitting that slows the water way down (not nearly as much fun)

after cleaning the wheel (and painting) be sure and orient the paddle wheel with the axiss of the boat. The big split ring helps do this and some models have a notch that orients the pieces. Be sure to righted the retaining ring  

some bottom anti foul paints are not friendly to plastic. So only use one that is for sensors or says it doesn't harm plastic

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Les & Trish Troyer
Mahalo 
Everett, WA
1983 C-36 Hull #0094
C-36 MK 1 Technical Editor. 
mholzmann's picture
mholzmann
Last seen: 4 days 34 min ago
Joined: 6/12/08
Posts: 51

Thanks for your comment!  I first started reading your response which said you have it down to a pint.  I thought, yeah right.  But then I re read and understand the fact that the left hand immediate covers the hole. Then you slide your hand away with the plug.  Brilliant!  I probably like many would pull the meter and then try to quickly jam the plug in against the resistance from incoming water.  It works but a little more water than a pint.

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Mark Holzmann
"Hawkwind"
Sail #1246
Rose City Yacht Club-Portland OR
Catboat Willy
Last seen: 16 hours 53 min ago
Joined: 12/22/14
Posts: 107

Paul; There are several rebuilding kits available from Airmar (Makers of your transducer)  to replace the various wheels in your transducer. The rebuild kit you'll require will be dependent on what version of Airmar transducer you are trying to rebuild and what series of instrument you have. There is a very good description of which one you'll need on the 'IMarineusa.com' web site.
Try  http://www.imarineusa.com/airmar33-493-01paddlewheelkitforst-800.aspx they  are about $30.00
Airmar 33-493-01 Paddlewheel Kit for ST-800Airmar 33-493-01
or

http://www.imarineusa.com/search.aspx?find=paddle+wheel
to see the entire listing of paddle wheel rebuild kits.
Bill

 

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Bill Dolan 1990 Catalina C-36 MKI - Hull #1041  'Williwaw'
Std. Rig, Walk Through, Wing Keel
M35, Oberdorfer Conversion,
Home Waters; SW Florida
'You are never out of work if you own a boat'

 
pkeyser's picture
pkeyser
Last seen: 5 hours 13 min ago
Joined: 5/18/13
Posts: 241

Thanks all. Good info.
I pulled the sensor today. Found it teaming with little sea creatures and wrapped with very fine seaweed. A tooth brush took care of everything. I do have a lot of slop between the wheel and pin though and will order a new one from the info in these postings

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Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

pkeyser's picture
pkeyser
Last seen: 5 hours 13 min ago
Joined: 5/18/13
Posts: 241

Mark-
Our Ray Marine speed transducer is designed with a flapper. When you pull the transducer from the hull, the flapper dramatically slows the inrush of water. It also came with a blank pug that screws into the transducer housing to stop the water flow while you work on the transducer. You can definately perform this with minimal water entering the bilge- a pint to a quart maybe. Our 1986 C30 had a transducer, that when removed, allowed a 2-3 foot geyser to gush into the hull; there was no flapper. I had a blank plug, but by the time panic resided and I screwed it in, many gallons had entered the bilge.

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Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

mholzmann's picture
mholzmann
Last seen: 4 days 34 min ago
Joined: 6/12/08
Posts: 51

Yeah I've had my boat about 20 years and I have pulled the unit to clean it several times I just thought Les Troyer's technique was clever.  I am not as lucky, no flapper. Just a big hole that's can be intimidating!!

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Mark Holzmann
"Hawkwind"
Sail #1246
Rose City Yacht Club-Portland OR
pkeyser's picture
pkeyser
Last seen: 5 hours 13 min ago
Joined: 5/18/13
Posts: 241

Knot meter follow up.
Replaced the paddle wheel and hub axle with new parts. Spun it and got a good reading at the helm. Inserted the transducer back into the hull. Got a reading while underway, but it was low vs. the GPS. Recalibrated the the unit, all seemed OK, but the speed displayed seemed to vary quite a bit while underway. Cleaned the hull around the transducer with a pole brush. (The water in N. New England has been too cold this year to perform my mid season hull scrub.) Sailed again, and the recently recalibrated unit display a speed much higher than GPS speed. The bottom line is that growth on the hull was having a major impact on the flow over the impellor. Relacibrated the unit after the hull was cleaned, and all is well; the GPS and the ST60 yield the readings in water without a current. 

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Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

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