I am in the process of putting in a new knotmeter
made by Moor electronics (model #LKD) which cost $180 at defender.com (paddle wheel transducer and digital display unit that requires 12V input). Our old knot meter required about 1/4" through hull hole which was propeller based and fouled up easily over the season. This one requires a 2 1/8" hole in the hull for the sleeve for which I have attached a backing plate. The actual paddle wheel transducer is probably about 1 3/4" in diameter that fits inside the sleeve. I am guessing but I believe that the actual paddle wheel is about an inch in diameter. One nice thing about this unit is that they supply a dummy plug which can be put in when you remove the transducer to clean it. Another nice thing is that the receiving display unit is digital and applies averaging to the signals (but the display unit was larger than my old needle display unit which would sway, sometimes wildly or not at all). I would not recommend that you use one brand transducer with another brand display unit but cant say why. Of course I am still in the build-in phase with this unit and cant comment on its actual usage yet. Good luck. CalebD Tartan 27 #328, 1967
