CONTINUOUSWAVE

Sorry for the confusion on the speed! I do mean (nautical miles per hour) I went back to the dealer today and exchanged the props for a 13 1/4 x 17 pitch Aluminum Yamaha prop and tested it out. [The boat was] able to reach 35-nautical-miles-per-hour [with the engine at] 6,300-RPM, and was able to cr...

Thanks Phil T, I have seen that prop name come up a lot amongst the forms. Jimh The speeds I gave are in naughts. The gear ratio is 2.33 as you stated, The RPM full throttle range is 5300-6300 with 5800 making the full 70HP I was able to test the new 13 5/8 x15 prop today and noticed a decent increa...

Recently I was able to upgrade the engine on my [1987] 15-footer to a new Yamaha F70. The dealer gave me a 13-1/2 x 14 pitch propeller to try out, and, as I suspected. [the engine] was very under-propped. [The engine accelerated to] 4500-RPM [and the boat speed was] 21-nautical-miles-per-hour]. [The...