RPM wise, what would a 4 blade compared to a 16.5x28 merc 5 blade be? The 5 blades are merc cast, not cnc versions, what rake were they offered in? Lastly, how much RPM can be gained by reworking them, they are box stock and untouched right now. Thanks!

I'm not sure what your asking on the first question but if you are asking what propeller in 4 blades would run the same RPM as a 16.5x28 5bl. I would go to a 17x28 4bl.

Some shops like to use pitch to equal out rpm between numbers of blades. I lke to use diameter first and pitch second for various reasons.

The advertised rake was 15 degrees. However, due to some manf. issue we had, they usually ended up at 14-14.5 degrees of rake.

We can gain 300-500 rpm depending on the recipe and cut we use. We determine the best route via your boats current performance and personality.
If they are box stock, there is tons of room for improvement.

Back in 1999, Dennis and I decided to stop offering stock #5-6 propellers because all the stock ones came back for Labbing anyway. (true story)


Brett

Hey Brett. The numbers stamped on one of the props is FB1SL. 16.5x28 Merc. They are satin finish, and although appear to be stock, I notice all the very tip of the blades appear to be curved, as if the cupping continues all the way to the tip of the blade. The tips of the blades are "pointier" than the 17x29 merc four blades I have, if that makes any sense whatsover. As if, you bumped the tip of the blade, these would puncture your skin like a knife, where the 17x29 four blades don't look or feel that way.

I guess what I am assuming is these could be labbed from the factory? I was told they were bought from merc, tried once, and taken off.

They were factory Labbed at Merc Racing in Feb. 2006
They are a standard template Lab.

Brett

Got a chance to run them. Too tall for me right now. 4600rpm wot and 74mph. 1.5 ratio drives. I really need to be 5400-5500 wot. One thing I noticed, my boost was at its max (5psi) at 3500 and above. I also didn't seem to care for the handling. It almost seemed like it wanted to Chine walk at max speed. Probably because to get any speed and rpm I had to trim it to the max. Although the 4 blade 17x27 I needed to trim out to the max also, but the 4 blades seemed to handle better at wot.