17", 3 blade. I considered an 18", but not sure about cavitation tip clearance. I have had cavitation before, and want to avoid it. I figure with the Max prop being slightly less efficient, the 17" should be similar thrust to what I have now for a given RPM, and I can up the pitch for better speed. I have a 60hp Volvo engine, so a lot of room for both bigger size and pitch. Hoping to be able to cruise at 7+, and make 8kts all out. (I can just make 8kts now, with lots of cavitation, but cruise 5.5kt-6kt)
I also considered the 4 blade, which is what PYI recommended with my huge engine. But I want good fuel efficiency. Motoring between Panama and SF (which was like $1000 worth of fuel) I got 0.4 to 0.5 gallons per hour at 4.5-5kts. That goes up to only 0.6 at 6kts. That seems a lot better than what those with Yanmar (even new ones) and Perkins report. Since I am likely to be motoring some long distances again, I want to reduce the fuel on my foredeck.
Yes, I have a drive saver, there wasn't enough room for a standard sized zinc prior to my installing it (I had to use a low clearance collar) and I had massive cavitation that was reduced by moving the prop aft.
I shouldn't need a shaft zinc? The prop has one of it's own. But I do want the prop to be positioned towards the aft of the aperture for less cavitation and better performance. Certainly at least center and not forward of it. So I hope I don't need a new shaft. That would add a lot of extra cost, not only from the cost of the shaft and fitting it, but time on the hard. The last thing I want is to be stuck on the hard for weeks or months waiting for something like that. In 2016 when I last had the shaft out I called around locally to have it checked out. There was a 6 month wait for that type of work.
Excluding the location of the larger hub, are the blades in about the same position as a standard prop?
Not going with a dripless system. While it might be nice to not have water in the bilge, the packing is 100% reliable and can not fail. I have graphite packing, which is almost dripless. It is dripless when not spinning.