I am running a 3.3L 250 4 stroke Yamaha on a hewes 2015 220 OP ETHT. The current prop is 15-1/2 x 17T Yamaha saltwater series II SDS. I want to stay with the SDS as it shifts very smooth. 3 guys, 2 dogs, 3/4 tank of fuel and deeks and guns etc. I WOT at 6100 and 44mph. With more weight/load I hit 6000rpm and still at 44mph.
I'd like to increase speed and fuel efficiency if at all possible. Yamaha's prop selector is telling me to go with either a 15-1/4 x 18 or 15-1/4 x 19. Their site says 150 +/- 50 rpm for each inch of pitch. I think that I should maybe try the 19 pitch in the same model prop and maybe I can get a little better mpg. It does good now on mpg - I averaged 3mpg over 100 hours use last summer. Thoughts?