How much can 1/4" diameter diff in prop size make?

[scfan]

My prop was stolen over the winter so I am buying a replacement for an '03 Yamaha 250 HPDi on a 23' Seacraft. The old prop was a 4 blade stainless 18" pitch with 15 1/4" diameter which ran at 5200 rpms WOT. Yamaha recommends a 17" pitch with a 15 1/4" diameter, which should get me up to 5500 rpm which is the recommended WOT. My dealer has a 17" with a 15 1/2" diameter and I am wondering how much a 1/4" diameter would make if anyone has any opinions experience, thanks in advance