My results were from trying b4s and b3s that I had more out of the hole power with b3s especially with a full load , but higher top end with b4sFor what it is worth, I had B3's on my 1979 Skipjack 24 FB with 5.7 VP and 280DP. Sweet spot was 22-24mph at 2.2mpg. I have B4's on my 1990 Skipjack 25 FB with 5.7 and 290DP, probably getting less than 2.0mpg. Got me thinking now, maybe I should drop down...hmmmm.
Wow maybe I need some head work too, I get max 4400 doing 30 knots or so. My sweet spot Is 3000 too , burning 7 gph and doing @ 17 knotsIt's had head work done,I believe 525is rpm is redline. Sweet spot is 3000rmp cruising speed. I'd say 2 mpg. It's got a stock cast iron hi rise intake and holly marine carb.