Absolutely: How much money do you have? How much do you want to spend? That’s pretty much what the final answer comes down to, but let’s try to make it easy for you. First, the pitch of the prop (normally in odd numbers: 15, 17, 19, 21, etc.) is used to bring your engine to the midpoint of the operating rpm with your normal load. If your normal load includes a dog and a cooler full of drinks, that load will be different from Aunt Minnie (200 pounds) and Uncle Bill (150 pounds, wet). The qualifier is “normal.” If the operating range is 5000-6000 rpm, the pitch selected should have you at 5500 rpm, full tank of gas, safety equipment, etc. Anything less than 5000 rpm will be putting an unnecessary load on the engine; anything more than 6000 will be wasted rpm with a loss in power and could damage your engine. The diameter of the prop generally goes with the selected pitch, so you don’t have to worry about that selection unless you’re a purist or performance freak. Now, stainless or aluminum? If you’re hitting river bottom continually, go for aluminum. The gears will thank you. If getting a little extra speed out of your boat on the way to the offshore fishing grounds is worth $500 more than an aluminum prop, go stainless. Hope this helps.