Do surface drives require the same gear reduction seen in Bravo's? I see where they run 1.65, 1.50 or 1.32 if not mistaken. I believe the last two ratios are what's most common. What is right for a surface drive?

Depends.,... Yes you will need a reduction ratio. That's what I've been eluding to with the V Drive and other means of dropping the engine output to the drive units. What rpm your engines will turn, what hp they will make, what the displacement of the boat is and so forth.

What are your engines? Cannot accurately make out from the pictures.

The engines are late model Chrysler Hemi with a redline of 6500 rpm.

Thought they were.. At first assumed LSA then the spark plug hole made me thing Dodge.

In the various searches I've done it seems most guys redline their engines in the 5500 to 5800 rpm range, maybe 6000. With a 1.5 ratio that gives us a prop speed of 3667 to 4000 rpm.

One of the options that exists here is using the 1.76 1st gear ratio in the powerglide. With an engine speed of 6500 rpm that provides a prop speed of 3693 rpm. If we increase the engine redline to 7000 rpm the powerglide gives us a prop speed of 3977 rpm. This puts us square in the prop speed range of a typical Bravo set up.

What makes this option interesting is the powerglide has the same 1.76 ratio in either low gear forward or reverse gear. That allows you to select prop rotation by simply shifting into the appropriate direction. I've spoken with a few drag race transmission builders and they have confirmed there is no mechanical reason to prevent you from running the transmission in low or reverse. Just watch out for a slight increase in running temperature which can be handled with appropriate cooling.

This solution seems almost too easy which means I have to be missing something. That's why I was curious about proper gearing for a surface drive. What's the typical prop rpm for the Arneson set-up?

There is no "typical" and if you can make the powerglide work then it works. It's that simple.

Only constraints you have to look at is propeller pitch to reach your speed goal. To slow of an rpm will require a larger pitch so you have to do the math to make certain you don't paint yourself into a corner just b/c something seem's to good to pass up.

5700/1.76 with a 40" wheel yields 110 mph so your safe with this combination..

Thanks for all the input.

A 40" wheel isn't exactly common.

Yeah, I recognize that. I think gear ratios will be something I'm going to have to mess with no matter what. With the 6500/1.76 combo and a 34" prop that equates to 107MPH. That puts me square in the target but prop selection is it's own black art. We'll see what happens as the project develops.