some drive ratio explaining
 

hi all, whats the diff between a 1.50 and 1.36 and which application are they best suited for......can you have 1.50 lower and 1.36 upper(guessing not:party-smiley-004:) want change from b1 to an xr and want to no which setup is better...its 26' pq with about 540hp n 580lb tq thanks

.14, I couldn't resist. The ratio is the number of turns of the input shaft in comparison to the output shaft of the drive. 1.50 turns to 1 turn verses 1.36 turns to 1 turn.

Unless you want to buy new props, keep the same ratio you have now. Not sure, but I would think the 1.5 would have more torque on a prop verses a 1.36. But when you change props to get the same speed result, I would think they would cancel each other out. I would think a 1.5 would have less stress, making the life of the drive last longer. I'm no expert.

There's no reason to use anything other than 1.5:1 on a V-bottom unless you have enough power to run out of prop selection, and by that time, you are going to be blowing bravo drives. Cats are a different story.

ok cool, i was looking to buy an xr lower with 1.36 gear ratio from the classified sec here(real good deal) and then try and find an upper but will keep looking for 1.5 thanks

On most drives, part of the reduction happens in the upper, and part happens in the lower unit. Multiplying the two ratios together gives the overall ratio. For instance, a typical SSM IIIA or V has a 1.31:1 upper and a 1.125:1 lower for a 1.48:1 overall. Typical Bravo has 19/16 = 1.1875:1 upper and 19/15 =1.266:1 lower for an overall 1.50:1

Fixx
 

A 1.50 drive ratio will make the boat accelerate quicker to its speed,a 1.36 ratio,,wont be as quick to jump on plane as the 1.50 but the 1.36 would be a stronger as to the 1.50 ratio..

would the transom assembly needto be changed as well

No.

You would also need to drop about 3" in prop pitch going from a 1.5 to a 1.36.
Like was said, no reason to switch to a 1.36 unless you are running out of prop sizes, which you shouldn't be with your combo.