On Mon, 17 Aug 2015 10:27:40 -0400, Justan Olphat
wrote:

1. The Big Foot is a workboat motor

It is certainly not for "performance" as much as giving a good push at
a relatively lower speed.
Yamaha must only make workboat motors tho. My F70 is swinging the
exact same prop as my big foot used and that is the only lower they
sell.
Alternately you could argue that at 60-70 HP, you should be in the
larger prop. The difference between my F70 and Don's 60 are minimal
and 3-4 HP at most. That is from a little better breathing on the
intake side. You will only see that at WOT. I have about 0.3 hours at
anything even close to that.