Got my recommended prop size today from the engineer

[saburke17]

Hello Sean

As discussed over the phone

4 blade Nibral 21 x 25 73% bore 1.50

$1709.35 each

So I don't have an exact weight on my FBC but its Definitely lighter than stock as the inside was gutted and now its all fiberglass instead of wood. No holding tanks or genset. I put the weight at about 12k pounds and this is what he came back with. He said if the 21 was to big i could drop to a 20 x 26 4 blade. Thoughts? I've blinded myself looking at post here on props and it seems the norm is 20 x 22 ish? 4lha-stp with 2.04 to 1 ZF's 1.5 shaft. is the 73% the efficiency of the prop?

[Craig Mac]

Pitch sounds high-----but will differ to the diesel guys.

As mentioned in an earlier post----the blackfin website has compiled a worksheet of boats listing all relevant info --I think we should start one as well---I don't know how to post on this site but will forward to anyone that can.

[mike ohlstein]

26 is high. You're going to idle at 8 knots.

[Tony Meola]

Some of the diesel guys are turning 21 inch props. The norm on here tends to be almost square with cup. I am running with 270 Cummins 4 Blade 20x23. The guys that go up to 21 are probably turning 21 x 20 with the same engines. The key is to hit the top end at the RPM's the manufacturer specs for the engines. Most of us actually are turning 50 to 100 RPM's over the specs the manufacturer sets. This keeps the engines from over working and extends their life. It allows to hit the spec RPM's when the boat is fully loaded with people, bait, ice and whatever else you decide to pack on board.

[saburke17]

https://www.dropbox.com/home/31%20Bertr ... 190423.pdf