Quote Originally Posted by stupidbaker57 View Post
I've been down that road with respect to the motorcycle having a transmission that would require shifting. The Honda engine I have is from a cb400a. It has an automatic trans, low and high. I have the drive designed as low as possible in the boat but I am not using a belt. Since the engine will be sideways, the sprocket is off centered to starboard. (31 years in the navy and I think it's still the right side) Power comes thu a 5 inch jack shaft and transmits the power to the sprocket (see pic) via chain. This is where I can change ratios to speed up or slow down the prop shaft to better match HP to speed. Rough figures put this at 50 mph with a 27 hp engine, a 16/21 ratio running 7000revs with a 7X10 prop.
If this doesn't figure right to you, it might be that my figures on the cocktail napkin got blury when I spilled some beer.
In terms of what your working with seem to be within reason & workable. It will be an interesting moment when it up-shifts. I was thinking 2 stroke at 1st but guess this is a 4?