RE: how fast would this go?
In a 90cm Boat, Hydro? Cat , Deep V??
What did you have in mind
Did you want to Run a Twin Prop Set up or a Big Large Prop?
What Goals Did You want to Achieve ? How much Money will you throw into Building the Boat?
As Is a Double Turn 8 with Correct Prop Size and Dead flat Water in a Deep V Hull could Hit a Theoretical 50kph but there are too many Vairables to give an Accurate answer..
Tell us what You intend to run so we can give you a Ball Park Figure