Thanks for the information. Yes, the 130's may be the right motors. They are only 15lbs more than the 115's, I'm not sure about the cost difference.
I turn 6000rpm WOT with my 19" props. Years ago, a buddy of mine that worked at OMC brought me some 4 bladed 15x21 props to try out and they were incredible. I got the same performance as my 19" props at 10% less RPMs. I could get up on 1 engine too. I beleive 10% less RPM translates into 10% less fuel. That would have pushed me to a whopping 1.2 MPG instead of 1.1 MPG. The props were pretty expensive but would be a great consideration.
I did find this Twin 115 Etec performance paper:
Etec twin performace stats
It is a bigger aluminum hull, I'm not sure how that translates to a seacraft hull but 3.1 MPG sounds good.
Here is a picture:
Another:
