Virtually every sailing boat built in the last 30-40 years will have a more than adequate engine to allow you to motor anywhere that you want + generate all the battery power etc that is required. In additiona - as a sailing boat you will be able to unfurl the sails ( or hoist if more labour intensive) and enjoy the peace!!
Most MOBOs seem to be built on the assumption that you want planing speed and by definition will cost a lot. 2 engines are twice the servicing of 1, MOBOs of the liveaboard size seem to have engines 100hp + a sailing boat will be 40hp - maybe 50. Thats less maintenance and less fuel.
As others have said - if you have no experience , charter first - or at least see if you can cadge an experience trip on other peoples boats, then spend your money