1997 C80 Prop?

[Bloodhounder]

I am trying to figure out if there is a "right" prop. The engine is on a 20' pontoon boat. I usually run with 2 adults and 2 big dogs and 28 gallons of fuel. Currently I have a Piranha 3 blade 14x13 prop. I can't recall what the original prop was. I do most of the cruising at 3200-3400 rpm and move along at 15-16 mph which is fine for a cruising pontoon. Open throttle gives me around 4800 rpm. I don't recall the speed. The service manual says I should be running wide open at 5500-6500 rpm. Am I straining or hurting the engine with this prop? I read somewhere that it is "imperative" that you have a prop that will allow the engine to run in the max rpm range. Yes/no? I believe I am getting better gas mileage with the lower rpm prop but I don't know how much better. If I went to a smaller prop with less pitch I believe I could kick up the rpms into the spec range but would lose on fuel consumption. Does anybody have any ideas or comments on proper prop size for my floating living room? I don't want to trash the engine to save a buck on fuel.

[<boats.net>]

The engine does need to run in the operator range.A pontoon boat is not a plaining type hull and changing props shouldn't effect fuel comsumption that much