We have a 7.5m fibreglass fishing boat with a pair of FT50CET (high-thrust) outboards. The motors are going well over 6,200 revs at close to WOT (haven't pushed them all the way) and the boat is barely on the plane at around 18kts. It will do 15kts on just one at 5,800 with no airing/cavitation. Been looking at the Yamaha prop-calc page and it looks like we should up the pitch to 13 or 14. Can't buy them where we are so I'm looking to buy online. But I can't find anywhere (Yamaha site, Owner Manual or Service Manual) what sort of prop we should buy: 14 or 15 spline? Thru prop exhaust? Hate to buy one and then not be able to install it! Can anyone advise?
