Re: overpropped vs underpropped
jrd22 has it right. I see that many still have the opinion that putting a bigger prop or a steeper pitch in your prop will reduce engine wear and save fuel, and they choose to disregard engine manufacturers and mechanics. Everyone thinks they know better. You all can do whatever you want with your boat, but I think you'll find that with the correct or slightly under-pitched prop you will get the least engine wear and the best fuel economy. Yes, with an over-pitched prop you actually burn more fuel and can't develop full horsepower.
The analogy I like to use is: having a boat with an over-pitched prop is kind of like riding you bicycle in high gear (you know how hard it is on your legs, well it's like that for the engine that is over-propped).