Thanks guys for all the info. I am new to all this blogging stuff so bear with me. Thanks again I will have to investigate that gear ratio change further. Is there a good reference to matching drive ratio, prop diameter, and engine speed set up?
Don't need, the manufacturer has already done that for you. The ratio supplied with any engine is based on the most likely size boat that engine will be fitted to, with the target of getting the right prop to be in the 15" to 23" range.
Hence the small 4 cylinder engines get the 1.94:1, the old 470 got a 1.84:1, V6s are a strange lot, some are supplied with 1.84:1 and some with 1.62:1, most V8s get 1.50:1, except the 2bbl 305, which got a 1.62:1 (target is the same size boats as the 350 but as it develops less power and torque, a higher ratio was required to keep the revs up when running props in the target range)...
The 'exception' to all that is high altitude. Boats used in high altitude are generally given the next highest ratio. Less oxygen means less power and torques etc, etc....
The reason for the changes with the V6 is due to a couple of things. The power output of the V6 has increased quite a bit over the years (started life as a 175, now the 4.3MPI is 220hp) and the target boat size for the V6 is quite varied. As small as 17', which would almost need a V8 ratio drive (1.5:1) to 23' plus, which likes the higher ratio, 1.84:1...
HTH,
Chris........
