Calm water drag 850N

Added wave drag for 2m seas 250N

Added wind drag for 20kts on the nose 350N

Total drag 1540N"

Do you seriously think 1540N (2 hp) will drive a 60 foot, 5 ton boat at 10 knots into 20 knot winds?

I once pushed a big boat with a 4 hp engine on a dingy (lashed to the side)  it took forever to get it moving. but eventually yeah I got it moving. Maybe up to 4 or 5 knots in perfectly calm conditions, but any wind and we would have been toast.

I bet your calculations are off by 9.8?  20hp driving a 5 ton, 60 foot boat at 10 knots sounds a lot more reasonable.  And most of the power boaters I know would kill to get that kind of performance. . .  20 hp is less than 1 gallon per hour.  10 mpg in a boat going 10 knots is very good and doable.  You are claiming you can get 10 times better performance than very good, the equivalent to 100 miles per gallon.

Talador