Is 90Hp enough?

[RCGrootveld]

In Holland (where we do have a lot op displacement vessels) the guideline we use is approx 3 Kw/T (m3) displacement to reach your hull-speed. The resulting figure being approx 60% of max. engine HP

So 30T would result in 30*3/.6 = 150 Kw

 

[MapisM]

Very interesting, and sounds reasonable.
Also having an engine normally working at 60% of its rated power does make sense on long range boats, even if continuous duty rated engines might run at or very near their max power for days.