splicing SignetMarine transducer with knotmeter

[Piotr]

I just purchased a SignetMarine MK 11 knotmeter (3-pin male plug). I'm planning on purchasing a replacement 3-wire SignetMarine transducer for it. The problem is that both have male plugs. I've contacted SignetMarine who suggested that a) They'll swag some kind of a plug to connect the two (no cost estimate), or b) I could directly splice the two. The problem is that, apparently, the third wire "doesn't do anything," but they ignored my questions as to the color of the individual wires I should be splicing.

On the flip side, the PO installed a 5-wire transome paddlewheel which does not have any plug and is not hooked up to anything. My understanding is that the sensor is likely a temp/speed combination. Is there a way to a) hook it up to my 3-wire knotmeter, and b) if there is, how to tell which wires are for the speed sensor?
Any ideas are appreciated.

 

[Bill Roosa]

Are the male plugs the same shape? Usually they have an alignment pin so you can't connect them incorrectly. Another way of saying that is if you align the two mail plugs you will see which pin goes with its mate on the other plug. You can then neuter the plugs (leaving enough on the plug side to determine each pins wire color and just connect the correct wires together. If you need an extension you can use the same procedure just add in the extension wire insuring you get the correct pins connected and the ground sheath too to protect the circuit from noise. Alternately you could go to radio shack and either get a set of plugs, neuter the old ones off and replace or get a small connection box (metal works great for connecting the ground sheath) and a connection buss to mount inside.
The transom paddlewheel/temp sensor will have two wires with low resistance (paddlewheel coil), two with high resistance (temp thermister) and a ground sheath. You can confirm the low resistance wires are in fact the paddlewheel by setting your multimeter to the lowest AC volts and while someone spins the paddle note that the voltage does go from 0 to some low value. You have to spin them pretty fast though so perhaps a can of compressed air (keyboard cleaner) to blow the paddle?? If you can get to the temp sensor you can place it in a pot of water and turn on the heat, then note that the resistance is changing as the temp changes. You could also just use your hand to warm it or pour some warm water over it if you can’t get the unit off the boat.
Alternately alternately, you could go to digikey and see if they have an exact replacement extension cable. They have most every kind shape and size of connector. I find the catalog to be easier to search though as it has lots of pictures so you can quickly id the connector you want.
Good luck