I have a chance to buy a 47 merc flattie tonight for a good deal (i think).

It is a complete motor and trannny. It's not stuck and has been filled with oil for storage. was supposedly running when pulled (several years ago).
24 bolt heads - casting numbers 59A-B
Casting on the rear of the motor is L363 and under that it says 59

I believe this is a 100hp stock motor and one of the best of the flattie family (i hear)

What's it worth?
and what can you tell me about it
Pro's & Cons?