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-   -   1.25 Ratio or 1.5 (https://www.offshoreonly.com/forums/drives-lower-units/225665-1-25-ratio-1-5-a.html)

picklenjim 03-05-2010 06:49 PM

If you pick up 600-800 rpm that would be perfect. 5600-5800rpm would be just right for a 600+ hp 540. And you'll be spinning the prop at the same speed as before with out loading down the motor so hard. That 5 blade may work just fine beings you were only maxing out at 5K before. Even if you need more pitch you can still run it, just watch the tach if you think it's going to rev to high. First things first,get the gears right and then check out the prop. Personally I think your going to be real close.

JohnSchiavarelli 03-05-2010 08:49 PM

The drive is just about complete.. might be able to test this weekend.. if not, next week for sure.. i still cannot believe i have been running a 1.25 ratio the entire time..

got the drive from Fred @ Trick back in 04.. before he turned into an a$$ and screwed so many people.. guess I should consider myself lucky it even lasted this long.

bajabob 03-05-2010 09:42 PM


Originally Posted by Griff (Post 3060455)
1.25 to a 1.5 and you will definately need more prop pitch. I would guess 1000rpms difference or more. I think 1.36 to 1.5 is usually about 600 rpms.

i agree with griff ok i did a test same boat same prop 150bravo 3600rpm 40mph 136bravo 3000rpm 40mph i like the 136 . i never take off full speed i think it is hard on the drive i throttle at 3000rpm my boat plane off nice . i never race at a dead stop. think about it you are crusing a nother boat come on the side of you . then you smile at them trun your hat around and push the throttle down. with the 136 you have to put a small pitch prop on the boats and prop it to the max rpm . i have a 1988 baja the bravo drive is low in the water i run 23 mirage prop. at 5400rpm . low 80mph me and my son and 50gallon of gas i trun 5600rpm . so if you are only at5000rpm and you put a smaller prop that going to bring your rpm up and you will go faster . .look at your dyno sheet were is the most hp at what rpm. take your highest tq number at that rpm add 1000rpm and that what i prop my boat . last year i had a 540 dart 624hp on the dyno .i redid it put more ponys in her . good luck i hope i help you out alittle:drink:

bajabob 03-05-2010 10:09 PM

john when i ran a 24 tubo prop it trun 4900rpm at 75mph it was a dog . slow on plane and to get to top speed . i then put the 23mirage wow what a diffrence it gets on plane faster midrange its like a rocket it is amazeing how fast i get to top speed. its funny how props make your boat run . i try 4blades and the 3blades work the best on my boat . can you get a 150 drive to try and put your prop on ?that combo make work for you . 5000rpm i dont think you are in your power band . your rpm should be a little higher?

JohnSchiavarelli 03-20-2010 09:11 PM

ran the boat last weekend and this weekend.. it is a totally different animal.. Idles so much better in gear.. comes on plane better.. mid range is wild. The RPM band has moved about 700 RPMS or so.. I have not gone full out yet but so far the 1.5 is way better than the 1.25 in all areas

bajabob 03-20-2010 09:22 PM

john are you useing the same prop ???post your top speed and your rpm

picklenjim 03-20-2010 10:53 PM

Glad to hear it John !! Looks like this summer is going to be a little more fun.


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