I am about the change the SS Yam Pro 21 x 14 1/2 (21-M) which I have on the 'NO LIMIT TOO'.
The reason, a friend who told me that apparently Yamaha says that this prop cannot go over 48 knots and the VERY strange way the boat behaved a few days ago while doing 45 knots and 4300 revs in force 5/6 and 1-1 1/2 mtr waves while racing with a few other RIBs.
I have looked to see what prop I can find to have higher top speed thus compromising on acceleration a little bit, which it does not matter very much any way as the boat is so light that it planes instantly with any weight on it.
I have made calculations based on 700 kgs boat weight, gear ratio 1.86 (26/14) and 147.1KW engine output @ 5500 revs max. I came to the conclusion that I should put a 4 bladed SS YAMAHA prop rather than a LASER or a SOLAS or any of the others. The prop I'm thinking of is either a 4 blade 23 x 13 1/2 or a 4 blade 25 x 13 1/2 Yamaha SS by also lifting the engine up one notch.
This prop, according to Yamaha, is recommended as an upgrade from the 21 pro for the 200 VMax. The prop is made (always according to Yamaha) for fast planning hulls with deep forward and shallow aft Vs. The prop is rated to reach a top speed of 60-65 knots.
As in Greece there is NO WAY that Yamaha will let me try the props and ion the US this prop cost $475.00 plus transport, VAT and customs clearance expenses and customs tax, I would like to ask if any one can tell me whether my calculations are correct and also if any one has any experience with this type of prop.
Ups just forgot here is the link http://www.boatsunlimitedny.com/Yamaha_prop.htm