ursaminor wrote:
The original engine on my boat was a 1989 3 cylinder Mercury 90 HP. Not sure of the gear ratio it had at this point (I replaced it in 2012) but the Mercury aluminum prop it came with was 21 pitch. That was fine for light loads, however I ended up going to a 19 pitch in later years. It would do 40 -41 on my hand held GPS with the 21 pitch.