i have an '09 with f350's. full fuel and water and a few people. i run a solid 1 mpg from about 19 to around 35 mph. this is almost spot on with the yamaha performance numbers. i'm using the new 4 blade props, which nick top end by about 5 mph (i don't care) and fuel economy by 0.1 mpg (that i could use) from the stock 3 blades. the control is unbelievable though.
it is very important to first use the trim tabs to level the boat and then trim out the engines to optimal performance. it makes a BIG difference.
next time you are out, get the boat on plane. take note of your rpm, speed and mpg (don't focus on gph, use the economy display). level out the boat with the tabs and keep an eye on the numbers. then tap the engine trim a second at a time. you should see rpm, speed and mpg all start increasing, without moving the throttles. keep tapping until numbers starts to drop off, then you are on the other side of the performance curve. wind and current will have effects.
try it, you'll like it :mrgreen:
my bottom is painted, but i keep it clean. this is my first large boat and i was surprised to see just how sensitive fuel consumption was to proper trimming.
ron