repowered tritoon prop confusion

[horizonlawn]

I repowered my 22.5 ft landau tritoon with a 150 yamaha four stroke, it had a 90 mere 4 stroke with a 14 x 13 prop that would turn 5600 empty. Now with the 150 I have a 15 x 15 turning 5600. It seems to me I should be able to pull a 17 with that motor, but based off the numbers I don't think so. Any ideas? The boat weighs about 1800 dry plus motor fuel and such, both props were solas al. I did gain 9 mph putting me at 37 mph. Any help would be great thanks in advance

 

[Rancherlee]

Re: repowered tritoon prop confusion

keep in mind you went from a 2.33 gear ratio on the 90 to a 2.00 ratio with the F150. So that 15 pitch on the F150 is equivalent to the Merc 90 spinning a 17 to 18 pitch prop. You actually gained 4-5 pitches @ 5600rpm.

As far as slip goes ( I think you said 28mph @ 5600rpm in another post)
Merc = 7% dang good for a pontoon, right at where I'm at with my little tritoon
Yamaha = 8% dang good again for a pontoon!

 

[horizonlawn]

Re: repowered tritoon prop confusion

I forgot about the gear ratio change, makes sense now. With the numbers on the aluminum prop is it possible to get away with 17 pitch stainless prop, there seems to be a better selection when you go to a 17