Well I see a Holley carb (good, better than EFI, cause all parts for the EFI are NLA, just make sure that it’s definitely a marine carb) and an MSD distributor, also probably better than if it was OEM (because parts for those are NLA), but like the carb make sure it’s a marine unit. Best bet is get a referral to a good marine mechanic and get it checked out, and, take a boating safety course. Yes you can get a drain plug at a marine supply place. The drain in the floor, that might be some kind of cooler not sure. You can run the engine on the water muffs but first out the outdrive down, & install the water muffs and turn on the water hose BEFORE starting. And shut off the engine before shutting off the water….
Winterizing well that’s a whole topic unto itself….