I'd be very cautious about parting with cash for this engine until you do a little more research. If the gasket has blown, then there's an underlying reason. Has the cylinder head been eaten away with corrosion allowing water to enter the piston bore? Warn piston rings allowing 'blow-by'.
Assuming the head is damaged (you really want to see this off before buying), you'll need a replacement head, a new gasket and cylinder head bolts. These are normally tightened in sequence from the middle out. You'll need torque settings. They have to be new bolts, as they're designed to stretch and are use once. Pull the thermostat (need a new gasket too) and have a look. Chances are there will be salt build up. Lightly brush the thermostat with a copper wire brush, lightly lube with a decent marine grease and refit.
Drop whatever oil is in the sump and refill with fresh. Because the engine is new to you and you've no idea of the last change, then replace the impeller too and gear oil. Any scoring on the plate, then refit water pump kit (including gaskets).
Finally you'll want to check the compression on all cylinders. Kit to test is fairly inexpensive. Remove HT leads to spark plugs and test each cylinder.
I'd also want to test the engine under load for leaks (water and oil).
Might seem like overkill, but engines have a way of letting you down when you least expect it. Good luck
Sula
breezy
