Outdrive Gear Ratio Question
 

Why would or what would be the benefit of chaning the outdrive gear ratios from the standard 1:51 to 1:35? I have twin 525's on a 32' Schiada. The builder is advising going to 135 vs 151. Thanks for any insight.

No need to change gears unless you cannot find a bigger prop.

i agree,dont waste your money

What props are you running now? What RPM & speed? With the motors you have & 1.5 gears, I would not think that you need any bigger props than 32 or 34's. As stated above only need to go to 1.36 gear ratio is when you can not get a prop that is big enough. You can now buy props up to 36". Why is your builder telling you this?

some guys around here change so they are twisting the gears and shafts slower ie less wear

because of cavitation issues with high pitch props

The props at 34" and over are not as efficient and they suck getting on plane.

I have heard that 1.35 gears are stronger. Is that true?

Along the same lines, let's go the other way. What are the advantages/disadvantages of moving "up" in ratio? Just curious...

I'm told that a (numerically) higher drive ratio and a taller prop will accelerate faster than a lower drive ratio and smaller prop. Why that is, I don't know.

Ive always been told that the optimal prop pitch, efficiency wise, was 25". Of course, that was many years ago before computers and 4 and 5 blades. I ran 1.36 drives in my formula sr311 and 25 inch props. It worked very well in that particular boat with my engines.

I think the prop pitch equates to how many inches the prop moves through water for each revolution, ie, 30 pitch prop moves 30 inches through the water for each full revolution. The higher pitch props may provide more top end but sacrafice efficiency and cavitate getting on plan. So.....use a smaller pitch prop for efficiency and improved hole shot, but turn it faster with the 1.36 gear ration. What do you think???