inboard engine
An internal combustion engine often mounted amidships that runs a drive shaft through the hull bottom.

inboard/outboard (I/O)
See stern drive.

Capable of being inflated either with air, as in a life raft or life vest.

inflatable boat
A type of boat with air chambers into which air is pumped either manually or automatically for buoyancy, some having rigid bottoms.

inner liner
Smooth-finished, molded fiberglass structure adjacent to the inside portion of the hull.

Device that changes 12-, 24- or 32-volt direct current (DC) from a battery to 120-volt alternating current (AC).