Have a Datamarine trio of instruments. Fabulous, old-school quality. Real instruments, not Chinese electro-junk. 30 years old, and still running.
Anyway, the knotlog speed suddenly started to be inaccurate. The paddle wheel was stuck for awhile with accumulated grime as it gets sometimes in the summer. I was going to pull it to clean it up, but never remember to do so until I'm already under way and see the zeros. Then when my diver cleaned the bottom, it started up again.
The problem is that it is now a knot on the optimistic side, reading (example) 7-8 knots when I know I'm only at about 6-7, or reading 6 knots when I'm motoring out of the harbor at 3\4 throttle, which is when I'm usually at 5 knots. The motor is barely even capable of 6 knots, which can only be done at full throttle with no head wind and a flat sea. Also, the GPS reads about a knot less. I'm aware of the differences between GPS and water speed, and it consistently reads variably less in different boat headings, tides and currents. And, it's just obvious from experience that I'm not going that fast.
I have since pulled the paddle wheel, and found no damage or anything at all different.
Any ideas?
Anyway, the knotlog speed suddenly started to be inaccurate. The paddle wheel was stuck for awhile with accumulated grime as it gets sometimes in the summer. I was going to pull it to clean it up, but never remember to do so until I'm already under way and see the zeros. Then when my diver cleaned the bottom, it started up again.
The problem is that it is now a knot on the optimistic side, reading (example) 7-8 knots when I know I'm only at about 6-7, or reading 6 knots when I'm motoring out of the harbor at 3\4 throttle, which is when I'm usually at 5 knots. The motor is barely even capable of 6 knots, which can only be done at full throttle with no head wind and a flat sea. Also, the GPS reads about a knot less. I'm aware of the differences between GPS and water speed, and it consistently reads variably less in different boat headings, tides and currents. And, it's just obvious from experience that I'm not going that fast.
I have since pulled the paddle wheel, and found no damage or anything at all different.
Any ideas?
