A few years ago I thought I heard tell of a speed log that used a sonar beam and reciever to measure speed, thus no moving parts and nothing to clog.
Have done some searching and cannot seem to find anything out there nowadays. Any ideas or recollections ofsuch a beast?
And when I said non-impeller...I did not mean the old VDO sumlog with the propellor-on-a-fin-driving-a-cable-type configuration. Have one of those...it came with the boat and gained us half a knot of speed when we retired it.