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Old 03-30-2012
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Re: Speed Log out by around 3 knots

Motor at a steady rpm up current for a measured mile--recording your time and the speed displayed on your log, reverse course, without changing your rpm and motor down current over the same distance again recording your time and the speed displayed on your log. Take your average time to determine your actual speed and compare that with the average speed reported by your log which will give your log error which can be adjusted out. Ignor the GPS which is meaningless with respect to speed through the water--particularly if, for example, your making 3 knots through the water into a 5 knot stream. Your GPS will tell you you're making 2 knots in reverse.

Alternately, buy yourself a "KnotStick" with which you can actually measure and calibrate your paddle-wheel knot meter quite accurately.
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