What kind of boat do you have? How much does it weigh appx with the gear you have on board?<br /><br />Check for markings behind the thrust washer, just ahead of the drive pin. However, the brass thrust washer & the salt ocean may have made those numbers illegiable.
Doesn't sound overly heavy to me. I think a 13" would do nicely & give you a good top end. You could get a 12" prop if you wanted better low end performance.
