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Update ; Got motor installed , told installer to go the three holes up diagram . Was emphatically told that mounting three holes up went against everything that he knows about installing , and was joined by a couple of other service guys who said the same thing , all the while looking at me as if I believe everything I read on the internet . I remember reading in Whaler Central that " whatever the installer says , DO NOT let them talk you out of mounting 3 holes up , which I quoted that quip to the installer .
The 13.25 x 15 prop from Powertech was a perfect match . After break in hours , I ran it up to W O T for a couple of minutes ( 300 lbs of me , gas , and gear in boat ) I hit just a hair above 6300 rpms . Boat planes really quickly and tracks straight as an arrow all the way up rpm scale . Thanks tedious .