Having owned a 1990 vintage 135 hp oil injected V6 merc similar to that one, I would not fear that engine at all. Mine had been submerged (12 feet below the surface) for 12 hours (previous owner mishap). The engine was brought to the surface and "de watered" as per mercury's procedure for submerged outboards. The engine was running within hours... All it needed was a new starter. It gave me 3 years of reliable service before I sold the boat.
If you like the boat and it suits your needs, make an offer... You'll probably sell the boat before that engine quits. All that being said, there are plenty of good outboard mechanics and parts supplies here, if it ever did give me trouble it could be fixed easily. Things may be different there.