bcdreaming, I had one of these props same size and pitch on a 99 year model yamaha ox66 3.1 liter 200 h.p.motor. I believe before this series there was the pro v series.When the 3.1 liter engines first came out , they had such excessively strong low end torque that the regular pro v series props would not hold up.They were folding if you barely tapped something idling. Some were even twisting them while loading on the trailer. Thats when yamaha came up with the 25m. Its a thicker beefier prop, which was suited for the 3.1 liter application. From what I remember this is a very good prop even on the 2.6 liter. The 25m has good hole shot, great lift and is great for top end especially on a big Merc. I think Im right, Thats what I remember. GlynnLast edited by NELA COUGAR on January 19th, 2008, 2:15 am, edited 1 time in total.