Need help for knot meter

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Harry

My Navco(Navico?)knot meter is missing a tooth on the speed wheel and will not work. If I spin it by hand it does display the speed, so I know the unit works. It' just the flow of the water isn't enough to spin the unbalanced wheel. I took the complete unit to the repair shop and they cannot find a replacement wheel. Of course Navco is no longer in business (now Simrad). Next problem is(according to the shop)the hole for the thru hull is "much" larger than most replacement units and making the hole smaller would be expensive. He suggested putting the old one back in just to keep the water out (I never had the "dummy" plug), and locating a new knot meter elsewhere. Like most,I hate the thought of putting another hole in by boat. I would REALLY like to find a new wheel! I'm wondering if it would make sense to have a machine shop make a new wheel? Might be cheaper than a new hole & unit. Any ideas? Thanks much.
 
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John Dawson

Option #1: Fix the hole

I think I would fix the hole by taking the unit out, beveling the edges and rebuilding the layers of glass like in a Don Casey book. In addition, since there is going to be a hole there again, I would add several large layers inside the hull for reinforcement and to tie everything (hull and edges) together. If you are not comfortable with doing it yourself, I wouldn't think having it done would be terribly expensive. Since its underwater, a simple epoxy repair with no gel or paint work should do.
 
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Bob

Add a tooth

Hi Harry, You should be able to model a replacement tooth-and balance the existing paddle wheel, good winter project. Paddle wheels use a magnet or metal built in to sense rotation - so making a new one will require building that into the paddle wheel. Good Luck, Bob
 
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Chris Burti

Try DIY

You might try this if you are somewhat handy. 1. Melt some candle wax in a small cup, like the ones that Crystal Light lemonade comes in. 2. Insert an intact paddle just up to the hub and let the wax cool. 3. Chill the wax in the freezer and then use a razor blade to seperate the mold into two halves along the thin axis of the paddle. 4. Carefully tape the two halves together being careful not to distort the mold. 5. Mix a small amount of filled epoxy, fill the mold and let it set up overnight. 6. Trim the new paddle to fit the hub and epoxy the paddle to the hub. Drill matching holes in the parts to give the epoxy something to 'key' to. Some plastics are very hard to bond. I'd probably fabricate a couple of pins out of stainless wire to reinforce the joint. If it doesn't work, you haven't lost anything but a little time and effort. Good luck!
 
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Bob Pattersen

Navico Replacement Parts

Try http://awmarine.com/, these guys bought out the replacement parts inventory of Navico after Simrad took them over. They should be able to get you a new paddle wheel transducer. Best of Luck! Bob
 
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Glenn Bollin

I'm missing a tooth too!

Been wondering what to do short of replacing the speed transducer on a BiData 40. Think I'll try a little dentistry while she's on the hard. Glenn WindWisp 26.5 Hunter
 
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Wright Ellis

I went low tech ...

... and bought a "knotstick." You trail it as you would a sum log and it is accurate. (I checked it with a GPS.) I got tired of fooling with the digital log and sealed the hole.
 
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Bob

You might get lucky

using a product made by Duro and sold by Walmart - Plastic Weld, found in the paint department. It is a two part epoxy that sticks to just about any plastic (or anything else) and can be formed and sanded or ground to just about any shape. If you rough up the surface and get it real clean, the stuff sticks real well and sets up with the consistency of hard nylon. Worth a try and the $2+ that it costs.
 
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Derek Rowell

Replace the whole sensor.

Try to find a transducer with the same diameter (they seem to be standard) and replace it with a whole new system. Cut out the old thru-hull (I used a Dremel tool) and seal the new unit in with 4200, or 5200 if you are brave. I have found alignment to be critical fore-and-aft if you want the same reading on each tack.
 
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Dana Barlow,C&C 30' Mega,trailersailor

Radio Shack has little magnets

Most of those paddel wheels have little magnets in the tip of each wheel arm,I have found the same little magnets at Radio Shack. If your going to make new arm or the hole new wheel it will need a magnet at the end of arm,note some have 4 arms but only 2 magnets cross from each other.
 
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Jim Honeyman

GPS

Scrap the knot meter and use a hand held GPS. This gives you the accual speed over land. Most of the hand held units read out in MPH of KPH.
 
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Harry

I have a GPS,

but I like to know my boat speed as well. Thanks to all for your input & suggestions. I haven't yet decided which way to go. At this point I'm waiting for the guy from England to respond to my email.
 
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john renfro

speed

hello harry, take your old paddle wheel plug apart, hollow it out,insert the new smaller sensor into the old plug,fill the void around the new sensor, and use the existing hole in your hull good luck john
 
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