Wilks

Fountain used 1.65 drives on the 42 fountain when the had mild power. I assume the larger pitch prop provided better performance. When going from 4 to 5 blade props there is around a 2-3 pitch lower to keep same rpm. Would going to 1.65 drives when going to 5 blade be better for top end performance because you could keep same pitch in props?

JRider

iTrader: (1)

No, keeping the same pitch and changing the ratio is rob peter to pay paul. The only difference being the characteristics of 4 vs 5 blades (slip and lift). Mercury only recommends changing gears when there are no more available prop pitches. with the price of gears and installation I do not see any advantage.

shepnic74

My gun has ssm 3 drives and my primary gear ratio I use is 1:40 but last year at the beginning of summer I had a problem with a drive so I bought a complete spare set of drives but they are 1:68. Tried 4 sets of props and no matter what seemed to be 3-5mph slower. Could be partially because with the 1:40 I get on plane easily but with1:68 there is so much torque at the prop I had to run larger diameter or it would just blow the props out of the water. So even though I am able to spin a much higher pitch prop I feel I lost performance if anything. Just got my hurt 1:40 drive back so needless to say as soon as the boat comes out of storage they will be going back on the boat.

Griff

I would keep the 1.5's and drop the pitch if you go with 5 blades.

I don't think you'd see any real differences in cruise or top speeds with gear changes and taller props.
I have the opposite. I spin 24's with 1.36's. No real differences with my speeds vs other 32 AT's.

14 apache

iTrader: (1)

You need to try the propellers it may not be 2-3 pitch numbers off. Going from a 4 blade to a 5 blade CNC prop might surprise you. CNC propellers are faster.

Griff

Wilks has a 38 Donzi with 575sci's and Bravos