Powercat 348 engine HP and top speed/cruise speed questions

[Kit_L]

The boat is a custom Powercat; 9.13m (30') in length.

The general question is how to calculate top speed of a power catamaran with different horsepower configurations?

I have had a look at the BAM calculator (Speed Calculator), which suggests that a pair of 40hp engines, assuming a total weight of 7,000lbs and using the smallest coefficient will have a top speed of 23 (no units provided).

I am assuming that 80hp will not be enough to get the boat on the plane, but what do others think?

[Pete7]

I think it will be the other way around. Certainly with outboards 2 x 40hp only equals about 60hp due to the drag of the second drive unit. A single 75hp outboard was always faster.

Can, 80hp plane a motor cat? small run arounds or motor boats need 15hp per tonne to plane (16-20 knots) so 4000 kgs of cat; possibly.


Pete