2 stroke engines use a crankcase to pressurize the air-fuel mixture before transfer to the cylinder. Unlike 4 stroke engines, they cannot be lubricated by oil contained in the crankcase and sump: lubricating oil would be swept up and burnt with the fuel.
Marine and automotive engine oils are not interchangeable. The two primary reasons for this are water and wear. Consider that corrosion caused by water is a primary concern for marine engines.