Smitty

iTrader: (1)

I am looking at a boat with 1.36 ratio drives. Lets say it has 575 hp per motor. I has 25 pitch mirage 3 bladers. It weighs around 8800 lbs. It's max revs are 5000 rpm. I cannot water test this boat at this time. It is a deep V hull. I am wondering a few things:

1 How fast will this boat go top speed as it sits now??

2 Will it be faster with 1.50 ratio drives and different props??

3 How fast will it be with the 1.36 drives and 750 hp per side and the proper props

4 Should I buy a sailboat (JUST KIDDING) !!!!!

jryan26

Well
I just sold a 1991 32 fountain. 540s and 1:36 bravos.
At 5000 with 25p mirages it read 80.3 on the gps.
The new owner turned the drives in and got 86gps with 27 hydros at 4900 rpms.

jryan26

What kind of boat are we talking about?

PatriYacht

What year is it ? Older Bravo's with 1.5 ratio had gears with thin floors. It was a common weak spot. Since the 1.36 gears had thicker floors, some people with high hp used them as an upgrade. Also, if you spin the prop faster, you're reducing the amount of torque going through the outdrive. Supposedly there is a speed loss with the 1.36 gears but I'm not sure.

Smitty

iTrader: (1)

All I can say is that it is a 36 footer straight bottom and it is a 2000 model year.

PatriYacht

I think by then all Bravos had the better gears.

monsta

I just finished re-rigging a 2004 36' gladiator, with 750 Zul engines. She weigh's 8000 lbs. Run's a 1:36 ratio with 30x151/8 labbed bravo prop's. She ran 103 @ 6000 rpm. Hope it's some help, and if you need help professionally with this machine, all we do is rig, re-rig, and re-power's. We are a custom rigging facility. Good luck.

Smitty

iTrader: (1)

Any other guesses???

cooltoys61

I ran some #'s on go-fast.com
78mph with 10% slip for 5000x1.36x25prop.
Also using another calc there :1150hp with 8800# and fairly fast bottom design 85mph
with 1500=97mph.
It's a good sight and fairly close to my boats so far.

Panther

I've seen speed reduction with the 1.36 gears. I remember swapping drives on a 42 Fountain with tripples. The boat was running 27P Mirage plus with 1.5's at 5500 rpms and about 85 mph. We switched to 1.36 gears and 25P (don't quote me on prop size, it's been a while) at 5500 rpms and only got 81 mph.