Re: Prop for F115
Basically. Props automatically reduce in diameter as pitch is increased. It's a total-blade-surface-area thing. The 17 of the same family as your 15 will probably be 1/4" or so smaller in diameter. But it's not to reduce the load relative to yours, but to keep the load about the same. The pitch is the more significant number of the two. It has a greater effect, although diameter certainly has significance as well.
If you don't already have two props, get the 17. Your car has a spare, your boat should too. I usually advise one prop for speed, one for towing. Consider your 15 a power prop and a 17 a speed prop. If you were considering a stainless prop, the 17 would be my recommendation anyhow. It would spin about the same RPMs as your aluminum 15 and give you another 2-5mph.
