[MariettaMike]

1990 Dolphin Superskiff with 2006 Yamaha 70 2 stroke.  Currently have 13 1/4 17 pitch prop but only turn 4500 RPMs on plane.  Will going to a 13 1/4 15 pitch SS prop help increase RPM's?   Also what kind of gas consumption or travel distance should I expect to get with an 18 gallon tank?

I am very happy with my 4 blade PowerTech PTR4 16 pitch on my 90 2s. I turn it 5200 WOT at normal trim and show 40mph on the gps. Trimming up increases RPM but not speed. Calculations show this prop has less than 2% slip running 22-32mph which is very efficient.

A 15 pitch may be a little too much for your 70.

If you call Powertech they will recommend their SCD3 "stern lifting" prop for the Super Skiff. That's what the previous owner(s) had pretty much worn out on my boat. 17PSCD3

You are welcome to try either of my props on Lake Monroe if you're in the Lake Mary area.