To figure out what electric HP you need first
start with the motor that WAS in the vessel. Usually
the manufacturers are pretty good a determining the
appropriate fossil fuel HP. Then divide by 3 for a coarse
guestimate. If you have enough room to size the prop up a
little, say from 14" to 16" then you can usually reduce
the HP to 1/4 instead of 1/3. If you list the current
engine HP, prop size, and displacement I could help you
even more. After gauging HP you can then use the
aperage/voltage to determine a burn rate and get the battery pack
sized right. This will require you to guess at a motor
technology and the voltage. It your trimaran is over 16,000
lbs you will probably need to call Solomon
Technologies and get an Electric Wheel motor. There aren't
many people producing marine motors much over 4 Kw.
