[Fr. Frank]

Originally Posted by FlyingTime

Fr. Frank,

We have been running Mercury racing 30" MAX5's from day one which are way to much. We'll be trying everything we can from 26 to 28" once we can get some on loan. Standard Bravo 1 and Bravo FS along with a smaller MAX5 is the direction we are going.

Best,
Steve

Using SOTP calculations, I conclude I don't have enough information.

You're pushing too much weight to run true surfacing propellers. So I expect a fairly sharp cupping near the blade tip, say the last 25" of the blade radius, will give you good bite with minimal ventilation (or blow-out).

It will have to be combined with a constantly increasing rake progression, such as is found on the PowerTech 15.25" diameter OFX and OFS series props. This enables you to run the prop semi-surfaced with greater stability. Not knowing the longitudinal CG, I'd recommend the OFS as a better starting point as it will have somewhat greater stern-lift.
http://www.ptprop.com/index.php?page...mart&Itemid=46

In those two series, I'm thinking the 4 or 5 blade for the extra grip the greater number of blades give. The 5-blade is a special order for either series, comes in up to 28"P and they want 3 weeks or so to make the props.

I know PowerTech used to make completely custom propellers, as they once made/modified a 15.25x16.5x3B OFS prop for my previous Seafari, which enabled me to just touch 53 mph at 6250 rpms with a '92 XR4 150 that had been internally balanced and polished to produce a bit over 200. Previous best speed had been with an old Mirage 17" and 46 mph at 6100 rpms. (I was running a 1.65 ratio lower-unit)

I had tried over a dozen props previously, and really thought the Mirage was as good as I was going to get, before Jerry Sciaccitano of AAA Outboard & Machine in Crystal River (now retired) connected me with Powertech, the company that was making his custom props for his racing Chrysler dry-stack outboards. I really like PowerTech.

I know Ken over at PropGods may be the most all-around knowledgeable guy out there, and has repeatedly proved himself willing to go out of his way to help people get the right prop for their application.

One note: progressive rake in a prop makes them quite inefficient in reverse!