Thats ATV and Motorcycle oil.
Boat engines and atv's are not the same engine by design. They rev differently and run under different loads.
I would not use it in your boat.
Try and sell it and buy the correct oil.
I would use what Mercruiser recommends or any good grade of oil you use in your car
1995 Maxum 2400 SCR 5.7 A1 G2 LUNA DE MIEL
1988 Bayliner 2455 5.0 IO (sold)
1987 Seaswerl 18ft C. Cabin 4.3 IO(lost in fire)
1976 16ft. Tahiti 2.5 IO (sold)