Prop Question

[chrisrub]

I'm looking to either refinish my prop or pick up a new prop. I'm running an OMC Sea Drive 1.6L. My current prop is a 13x17 stainless and I'm just not happy with my cruising speed.. about 18MPH at 4500rpm, and WOT is about 24MPH at 5500RPM.

Should I have this prop refinished (it does have a few nicks on the blades), or should I pick up a new prop? If I go the new route, what size prop would get me the best performance out of this motor?