I am very curious why you ask. This system has been out of production for a long time now. I too am a fond user, so I am also
concerned about the availability of spares to keep it running. It is much more accurate than the impeller type because it measures
water velocity beyond the turbulent hull boundary layer and it won't foul and wear out as the impeller type does.. I hope you
realize that it is designed to produce the same pulse train rate of the conventional impeller, as the electronics beyond the speed
box are interchangeable. So it shouldn't be rocket science, once the impeller pitch is measured. Please post your findings when
you have them. Currently, Sperry Marine make a much more sophisticated version for ships. That system measures flow in both the x
and y direction and can have multiple sensors on the hull. Its purpose is primarily used to measure water currents when inshore.
Steve

"Moonshadow" wrote in message ...
Can anyone please tell me how many pulses per nautical mile are delivered by the B & G Sonic Speed system.