Getting old Kenyon Knot Meter to work

[Brioche]

My boat has an old Kenyon knot meter on it that tries to work but doesn't. Once the boat is moving, the meter reads 2 knots, and doesn't change until I get up to about 6.5 knots, at which point it often jumps up to read 10 knots. So something is going on between the meter and its transponder, but not much. Since the boat comes out of the water every winter, I took a look at the transponder. The paddle wheel in it spins freely. It did have a little bottom paint on it, which I scraped off, but I doubt that makes a difference. I did note, however, that the paddle wheel is aligned at a sharp angle. It is mounted a bit fore of the fin keel, and faces more toward the centerline of the boat than fore and aft (angle of about 60 degrees). Kenyon is long out of business, but it would be nice to have a read on STW as well as SOG. This presents three questions: 1) Is there a way to check whether the knot meter itself is functioning correctly; 2) Is there a compatible paddlewheel transponder available; and 3) Is the alignment of the paddlewheel likely correct (it does seem unlikely that someone would have moved it). Thanks

[tkeithlu]

While I've had little luck calibrating the paddle wheel on my boat, 60 degrees off the flow of the water is definitely a problem. My guess is that the wheel is rubbing against one side of its enclosure, giving you an erratic reading.

If properly calibrated, a water-based speedometer will let you measure the difference between speed through the water and speed over the ground, which you get from GPS. That's useful information, but getting a paddle wheel speedometer calibrated is not easy. There are just too many sources of error in the sensor.

[tkeithlu]

Yes, align the paddlewheel with the water flow so it has a chance of working.

Then, find a place with still water and compare your GPS speed with your paddlewheel speed at various speeds. Mark your paddlewheel meter thusly. It is not likely to give you the same reading on both speedometers. But, then you can compare ground and water speed and have a pretty good idea of the velocity of the water you are in.

Maybe i'll go beck and try again on mine.

[Brioche]

Many thanks, tkeithlu. I will try aligning the paddlewheel and go from there. Your suggestion of re-labeling the knot meter readings is true genius. The sort of simple and direct solution that saves a lot of frustration.

[GordMay]

The paddle wheel must definitely be oriented for and aft [direction of water flow].

See also: “Testing Knot-Log Speed Instruments”
➥ https://www.cruisersforum.com/forums...tml#post164512

[bensolomon]

There is a setting screw on the back of the knot meter. Pull it out, and you will see it. you will need a small common screwdriver for the adjustment.