Consider this...
I don't think the extra weight of the four stroke will make a diff. in sailing/stability. However, when I was going through this same calculation last year, I discovered two things that tipped me towards buying a new two-stroke over a four. First, the weight-carrying capacity of your motor mount is not the only consideration. Four strokes generate so much more torque than a two, the mount must be specifically rated to handle four strokes. Mine wasn't. Second, my wife had enough trouble raising and lowering the weight of a two stroke; she definetly would have even more trouble with the added weight of a four stroke. The Admiral has always wanted assurances that she could handle and start the motor on her own; a four would have made that more physically difficult. A four will probably start more easily, run more quietly, use less gas and won't require you to mix fuel. Balance that against a lower initial cost for a two stroke, cheaper and easier service, lighter weight, etc.
