Has anyone used rotella straight 40W engine oil, I have some and not sure to use it or not. I don't use the boat below 60 degrees would this oil be recommended to use. Thanks

Fine to use.

Make sure the oil is good and warm before pushing the sticks hard.

Ken

I use the 15w40 to break in all my engines before switching to royal purple.....

It's all I've ever used in my non-roller cam motors (15-40 in car and 40w in the boat)

It is a 502 with roller lifters and rockers

It's a diesel oil, so it probably exceeds most "car" oil specs. It also has a lot more detergents in it because it's made for diesels.
The reason I put non-roller cam is that oils were reformulated a few years ago, decreasing zinc content (EPA regs). Cam manufacturers started seeing a lot of flat tappet cam failures and blamed it on the reformulated oil. Rotella was not reformulated and still has a lot of zinc. Cam makers reccomend it for flat tappet motors. Your 502 will be fine.

Rotella is a "goof proof oil", meaning that it also has an API SL rating, which means it can be used in gas engines.

Ken

It needs the detergent because diesels are sooty. That is the reason diesel oil turns so black.

Ken

Rotella has been reformulated. Zinc levels are down.