Seaplane with C90 / 7140 is turning up about 2550 in plow phase (not on step). Once on step RPMs increase to 2650. In level flight it will turn up to over 2800 RPM.

If I were to use a McCauley 7440 I expect to lose around 100 RPM. But, given the longer prop will 'off the water' performance increase?

What's the consensus out there? The common theme I've always heard was that the the longer the prop the better for seaplanes.