Not sure how to measure but its a 26 x 17 13/16 4 blade cleaver . Old one is cracked and I also need to drop 300 to 400 rpm's. This is on a single 32 velocity with 670 horse and the motor can turn 5800 if that helps . As soon as you start trimming the boat it is on the rev limiter.

I believe I have a pair of 18 x 30s if that will help. They are for small shafts not large shafts.

Thanks John, I will keep that in mind!

I have a 17.5 x 33 R for a #6 for sale if that will fit. Might be about perfect for you to drop rpms. Not sure if an adapter is needed to put in on a #5