The drive shaft is effectively vertical - so power it with either a windmill (how green would that be
? ) or a squirrel harnessed to a radial arm.
Viola, a REAL squirrel cage motor!
More seriously, glad you are still afloat.
A question - in you original pic of the motor there is a large "trunking" rising above the motor with an angled end. Is this the air intake?
Sucking air from low down in a boat hull is pretty hazardous, because of the possible presence of gas in the bilges. A good recipe for a runaway if the engine inhales fuel in the intake.
Following this thought along - a DC motor is an excellent ignition source with its commutation sparks - might be a wise idea to incorporate a bilge vent fan which would also cool the motor, esp. if you plan on 144V.
andrew