seamuspg wrote:II have a basic question to which I've seen varying answers. What is the oil/gasoline ratio for the 2+2 Mercury?
The oil-gasoline mixing ratio for a modern two-stroke-power-cycle engine is nominally 1:50, or one-pint oil for six-gallons of gasoline.
Almost all modern two-stroke-power-cycle engines have some method of storing the oil in a reservoir, and the engine fuel system will mix the oil into the gasoline. The mixing ratio will often be variable. This method is very common now.
In very old engines there would not be any internal oil mixing in the engine and thus no oil reservoir. For those engines the operator must continually add oil to the fuel tank in the correct proportion to the gasoline. This method is known as pre-mixing because the oil is already mixed into the gasoline before the fuel reaches the engine.
Automatic internal oil mixing was viewed by old-timers as a needless complexity on an outboard. Aided by much dock talk about failures in oil mixing systems, some engine owners would intentionally disable those systems.
The system used by Mercury was somewhat notorious for failing. You should review your Mercury engine to see if it has automatic oil mixing.
If it had oil mixing originally, verify it still does and it still works.
If it did not have have oil mixing or if a prior owner removed it, you will have to use pre-mixing.