La/stryker

I have read mixed reviews on gear ratios. which would be better a 1.5 ratio spinning a 34 prop or a 1.3 ratio spinning a 30? with the slip factor the same prop calculator shows them being within 2 mph. 6000rpm 1.5 34 pitch .085slip 117.8 vs 6000 1.3 30 pitch .085 120mph. (8.5% slip is what I have right now with 30pitch and 1.5 gears) is a lower pitch more efficient30 to 34? AND is the 1.5 harder on the drive than running a 1.3ratio with a smaller prop? I have heard thru the grape vine that a 1.5 with a big prop (34) is harder on the drive and more likely to break the drive shafts and or gears. any thoughts? btw big power (1100hp+)
and I know that any bravo style drive is very likely to break at some point with that hp, just wondering if one is a better choice than the other.

FIXX

iTrader: (2)

i like the 1.5 ,,it will get you from point a to point b quicker but 1100 hp.... yes the 1.3 would be stronger..you will also get more slip numbers with a 1.5,,brakes the prop loose easier..

Griff

What drive has a 1.3??? You are about of prop on Bravo style drives at 34" and I would swap to a 1.35 for more options.

BLUEMAGIC

With the 1.36 gear having less teeth then a 1.50 there is more strength. You got to find 1999-2000 desiel gears. These were the strongest gears produced. With 1100hp i would definitly choose the 1.36, after all with that kind of power your not going to b e able to take advantage of the torque a 1.50 gear offers unless you get sixs or arnesons.

La/stryker

A bmax does 1.3 and 1.5
Imco makes 1.35 and 1.5

dave269

Im also in the same situation accept only 900hp but currently running a zx w/1.5 & a 34p @ 6000rpm with about 12% slip. Was told that Im not efficient with this set-up and need to go to a 1.36 ratio. Can someone explain to me about efficient ??

BLUEMAGIC

the larger pitch props have a lot more slip then the smaller pitch props such as 28's or 29's. Back in the day before they came out with xr drives all the race boats ran bravo 1's with a 1.36 gear ratio. Having the power to turn a 34 pitch props puts a great amount of stress on the drive. Puts a huge amount torque threw the drive. Spinning a 1.36 gear allows to to spin a smaller wheel faster with less stress then spinning a large wheel slower. Also with a 1.36 gear you will notice a big difference in idle speed due to the fact your blade is spinning faster

J.P.

I run a 1.5 on my boat a 26 DCB Mach with a 32 bravo 1 and I can tell you it is a dog out of the hole, slips big time, tach will go to 35-3800 getting on plane and I need a 1:35 ratio also or a better prop. But in my mind weather you put a 34 on a 1.5 or a 32 on a 1:35 the stress on the upper would still be the same correct. Now if you went down to a 30 or smaller pitch on the 1:35 then I would say you are reducing the stress on the upper verses the 34 on a 1:5.

BLUEMAGIC

when running big hp in front of bravos its a good idea to try to do everything you can to keep it alive, every little bit helps. With more material on the 1.36 gear compared to the 1.50 along with the ability to spin a smaller wheel faster can only increase your chances of more boating hours.

launchpad475

iTrader: (1)

I went from 1.5 to 1.36 last year. I was limited to 5600 rpm from cam and heads, was running out of prop. The 30P had poor characteristics, and the 32P brought the RPM down but wasn't any faster. Only way for more speed was to turn RPM higher which I couldn't, or gear down and re-prop.

Now I run a 1.36 and a 28, fastest combo yet. My boat didn't seem to like the bigger pitched props.

28' Nordic, 540/Vortech