I had the 19" on my setup and could only max out at 5500 rpm"s. this was too low I was told so I switched to a pair of merc 17" 4 blade props and max out 5900 to 6000. I find the bite of the 4 wheels good especially at lower rpm and in rougher seas. i cruise at 3700 rpm, burn 14gph and cruise at 21-22knots.