I have a Delta Dash 5.5M with a Yam 130 two stroke on the back.
Blistering performance all the way to 42 knots.
Just about to do a retube and small refurb on her.
The max she can take on the plate is 140hp.
I agree though that a 90 is a good balance of power and economy.
At full power I use 20ltrs per hour!!!
Much less of course if I behave sensibly...............
But I rarely do!