If you're looking for the boat's manual, it's probably nonexistent.
If you're looking for the engine and/or outdrive manuals, post over in the
Mercury MerCruiser Sterndrives & Engines forum with your engine and outdrive serial numbers (year/make/model of the boat is irrelevant) and someone should come along and tell you which MerCruiser manuals you need to purchase.
Before spending any more money beyond the $100 you're into it, make sure you can get the boat and/or trailer registration transferred to your ownership. If you only got a bill of sale, some states make this process easy, and some make it difficult.
Also...here is some of the secret lingo used by some folks selling boats. This isn't always 100% accurate, but use this info to brace yourself / be cautious when you buy boats and boat parts in the future:
Bad starter = blown engine, cracked block, or some other mechanical catastrophe. As the buyer, you won't be able to hear it run with a "bad starter".
Soft spot / bad floor = waterlogged foam and rotten floor, stringers, bulkheads, and transom. AKA, this will likely be a full gut/restore for the buyer.
Runs on trailer = the engine will idle and run under no load while on the trailer, but there is some problem that will prevent you from accelerating when in the water.
New floor installed last season = likely a deck-over, AKA, they didn't remove any of the rot and slapped new decking over the disaster below to hide it.
