We purchased our 2002 Islander 270 new in March 2002 with a single 250HP OX66. The prop was the Yamaha Saltwater Series 15.25x17".
It worked pretty well - they are good overall props. But we were getting far too much slippage, so I worked with a local prop shop (Bay Propeller in Chesapeake, VA) to try different props.
We finally settled on a Powertech OFS4R-17. That is a SS, 4-blade, Offshore Series prop with a 17" pitch. Much better bite in sloppy seas, better hole shot, better mid-range efficiency, and the same top end (i.e. slightly lower RPM but reduced slip).
Find a local prop shop and see what they have that you can try, without obligation. With the understanding that you will pay for any damage. If you find one by working with them, then buy one from them - don't go out on the web to save a few bucks..
Disclaimer: I have no financial interest in Powertech or Bay Propeller.
Brian