That uses a Merc leg I believe a 2.30 gear ratio. Prop sizes 11",13" and 15" on typical pontoons.
I still feel that a 90 hp Force isn't likely to make 6000 rpm with a 13" prop on a 24 ft pontoon. also a little unlikely to make only 22 mph at 6000.
But pontoon speeds are all over the place for no obvious reason.Was 22 a gps speed?
I found some recent new 90 hp 2 stroke motor tests with about the same gear ratio 2.36 2, 22 footers with 15" props turned 5500 @ 25 mph,and 5150 @ 23.
2, 24 footers 13" 5400 @25.4, and 11" 5600 @ 23.5 these new 2 strokes rated at the prop highest rpm was an 11" @ 5600. And that with a
slightly easier ratio.