Originally Posted by beamishken
you could also fit a 1.65:1 ratio lower to your 2:1 upper which would give you a 1.65 drive.
I don't understand this I'm afraid.
If the input shaft at the top of the stern drive is doing a 1000 RPM and the top bevel gear is 2:1, then the shaft between the upper and lower bevel gear would be travelling at 500 RPM. If the bottom bevel gear is 1.65:1, then isn't the output shaft at the bottom travelling at 303 RPM which is an overall ratio of 3.3.
Do you not just multiply the ratios?