My guess is that hull
shape will travel at around 5 or 6 knots - more power will simply bury her backside even if it squeezes another knot
out (at the price of heavy fuel
consumption). If she was a ships lifeboat originally then never intended to travel great distances under power (anything fitted would be primarily about manoeuvring). My WAG is also around the 80hp mark (although another 20hp might not hurt) - the good news is that have space to fit just about anything you want in there!, would be sensible to plan the install before building the insides. I am guessing that budget
is not unlimited, so my take is that choice will be dependent on what is available / affordable - but wise to make sure that engine
and will gearbox
match, or at least a decent chance of finding a match.
As a double ender, from what I can see, looks like no engine
was intended, unless you fit twins ($$$) then will have a bit of "fun" installing a shaft centrally in a way that allows clean water
to flow into the prop (a single
offset is possible but will impact on "performance"). For a rudder
looks like will need a welder and some creativity.
Not sure what the trimaran idea is about - certainly won't sail as one. As a lifeboat she will be stable without outriggers / amas, but due to her bilge
shape she will roll a fair bit in a sea.
FWIW, me father had a wooden converted ships lifeboat (from a cancelled order) - only a 27 foot though. She had sails
on her (but not well enough to make a passage
with), under motor
she would plow through anything (but roll like a pig in a beam sea!) - but had more of a keel
that yours appears to. If you google
up a Fairey Fisherman will get an idea of what I am talking about.