Any tachometer that supports a 12 pole/6 pulse alternator will work for your engine. There is a calibration dial on the back of the tach. If it has a 6P setting, the tach will work. If you think about it, how would a water driven tachometer possibly be capable of measuring engine rpm? Ain't no such animal. The number from the prop you mention is of no use unless you include the prop manufacturer. Check closely, there may be other numbers under the prop nut or on the hub. The number may be something like this: 13-3/4x15.
