Which weight oil for my 1969 Starcraft 120 Mercruiser

[flyingd]

I have to change the oil in my 1969 Mercruiser 120 for the first time since I have owned it. I am curious on the best weight and brand/type of oil that would be best for it.

Thanks in advance

 

[airshot]

Mercruiser 4 stroke oil for inboard engines in the recommended weight by the people that made the engine. On my 1983 3.0 the 25W40 mercruiser oil is recommended and that is all I use. Any oil will work..................for how long is the question.......