An outboard on a boat this big will be a very unsatisfactory solution. While you may be able to come and go from a moorring, you will not be able to maneuver the boat near a dock, as the engine cannot be used alone. Plus as mentioned, the engine may be useless in a seaway.
With no engine, this boat is worth nothing. It'll cost you $4-5000 to put a new A4 in her, you can buy a P30 with a running engine for $5000 or so. Buy a boat that you can use, especially a first boat. If you do buy this boat, don't go over $1000, the seller will grab that and run.
Get a survey to find out what is wrong with the boat that you can't see. Otherwise, you will find out what's wrong with it the hard way, for example when it sinks under you and your family...
Certified...in several regards...