What determines your proper gear ratio?

39 foot boat, straight bottom, 25 degree dead rise.
0ld power 500 plus hp with a 1.5 gear ratio.


New power 900 + per side 588's. So in up
grading the drives to accomadate the power.

What factors help best to determine a good all
around ratio for Pleasure use?


Thanks
Cougarman

What were your old props? You'll be looking at a gear change around 32" of pitch.

As far as I know the only reason for a numerically lower gear is if you run out of prop options. Throttle up or BBlades over in the prop section may have a more educated opinion though.

Your most efficient prop is 28-32 on the bravo one 4 blades . I would try to use the 1.50 up to a 32-34 pitch and if ya need a higher pitch then go to the 1.36 and end up in the same prop sizes.


On My old scarab i started with a 1.36 gear and it did not make the speed the 1.50 did .

I asked the people at Hustler the same thing .A 388 hustler with a 1.50 gear and 30 pitch is faster than the 1.36 witha 26 pitch , its the torque multiples

I guess it could depend on the hull also.

Your WOT rpm is going to determine how fast you can go with the 1.5 drives. As a general rule if you start looking at having to go to 36 Bravo 1's you may start to consider a gear ratio change.

A good rule of thumb is to go with the 1.5's until you run out of prop. If you have engines that turn a lot of rpm you may be able to go 115mph before having to change the gear ratio.

Matt

If I'm understanding you correctly it responds and accelerates
quicker. Doesn't give it a quicker top end.

Which is fine cause most boating is midrange anyways.
On the Cougar I'm putting together is two of the drives
I picked up for it are 1.62's and the other drive is a 1.5 ratio.
I was also debating on whether two change two gear sets to
1.5 or to only change the one gear set to a 1.62 ratio.

I thought I was told the same thing, that with the power I'll be running in it ( tripple 720 hp. ) that I would like the midrange allot better with the 1.62 ratio. But if I ever bump the power up I would probably have to bump everthing back to a 1.5 ratio.


Thanks
Cougarman

I think I'm covered then ..... 454 mags 311 Formula .... 68mph ...... maybe one day .....

Great info though .....

I have heard that the higher you go in pitch(number),that the boat will sometimes handle different or may have a bad reaction to the prop.Meaning the higher pitch props have so much more flat blade surface that it will sometimes cause a hull to handle weird?The prop will actually cause the hull to move around more maybe?