1998 Johnson 225?

[Jetty Rocker]

Thanks for the info Ferm. I'm not sure if I have been using nautical miles or statute, that was a good point. I had been running a worn out 19p and my cruising rpms were 3500-4000. The reason that I went to the 21p was to lower my cruising rpms thinking that would increse my mpg's. I will start checking my mileage again and compare.

[THEFERMANATOR]

Originally Posted by Jetty Rocker

Thanks for the info Ferm. I'm not sure if I have been using nautical miles or statute, that was a good point. I had been running a worn out 19p and my cruising rpms were 3500-4000. The reason that I went to the 21p was to lower my cruising rpms thinking that would increse my mpg's. I will start checking my mileage again and compare.

You need to make certain you can hit at least 5600 with a good load in the boat, any less and your lugging it and milage will suffer. With a light load I can hit 51 MPH turning 5900 with mine, and that's with an APOLLO large diamter 17 pitch. I could step down to a 4 blade small diameter and probably hit 53, but my cruise would suffer. My first prop was a 15 pitch STILLETTO and when I ran it I had 200 carbs on it and turned about 6100 max running 48MPH, but my milage was only 1.5-1.6 NMPG. The large diamter got me ALOT more cruising speed and economy, and the bigger carbs got me my top end charge.