I am considering a change from 3 blade outboard cleavers to 4 blade ob cleavers. This is in hope of extending the life of my lower units. The boat is a 30 motion with 300pm motors with the propshaft 1 7/8'' above the bottom. The boat currently runs a best of just over 110mph at 6400rpm with 15x34'' lab cleavers Average day 105-107mph with fuel and people. What size 4 blades will I need? Wil this change extend the life of the my sportmasters,and what performance can I except?

Talk with Brett from B-Blades or Mazco props, they seem to have the most experience with outboard cleaver props.

I don't think Mazco has a four blade cleaver. They do have a four blade chopper.

Hello,

Yes the 4blades will help the Sporty's life span.

When we go to 4 blade cleavers we do 1 or 2 things to maintain the rpm levels. Because you will lose some.

The typical adjustment would be one of diameter reduction. However, with the height you are running on this specific hull we would suggest starting at 15" and we will adjust the thickness curve and the TE addendum's.

You will gain mid range acceleration, ability to carry more weight, better cruising speeds. The loss comes at WOT speeds. We can however get you close. It depends also on the current numbers. Heck we may be able to beat them.

Brett Thanks One more question... current props are 15x34 3blades at 6400rpm so with 4 blades 32''p or 34'' pitch?

If I remember correctly, you have non X's with the limiters @ 6700. If the engines truly make power to 6700, you can go to the 32's. However, these engines really only make power to the 6400 range. Therefore, sticking with 34's with improve your cruise speeds and shouldn't hurt the top end. The only advantage to the 32's would be the acceleration you would get.

I think your 3 blades are actually 14.75" diameter unless you have another set.

Brett You have a good memory I do have a different set of 15''x34'' 3blades. I have a line on a set of 34'' 4 blades if I get them you will see them soon
Thanks