Well I finally got out today. Ran the boat with the original 391536 prop. If you remember I had mentioned that this prop was pretty chipped up, so I ground off the edges and sanded them some.
Into the wind and against the tide:
1400 rpms - 5.3 mph
2000 rpms - 7.7 mph
3000 rpms - 9.3 mph
3500...