The Alerion 28 has option #99006 Marine Toilet in lieu of std. porta pottie w/Priv. Curtain.
I agree with mstern that an outboard is more typical and should be acceptable, but I'm thinking maybe jones2r already has power boat experience and wants to ensure plenty of power through the heavy currents when coming in and out of harbors. Once he's clear of the harbors, the motor shouldn't be an issue.