Hi, I'm looking at an '88 Liberator, 21 ft., with 350 Magnum V8, 270 h.p. Is this a Mercury/Mercruiser engine? Any particular problem areas with this boat or engine (beyond the "normal")? The current owner notes that the Alpha 1 lower unit needs to be replaced. What's a general ballpark $ for parts and labor for this? Any other maintenance recommended while putting in a new lower unit? Thank you for your time and advice. Larry