Have '02 Mercruiser 575's, 42' Cig; 80 hours on engines. Boat runs in fresh water. Was thinking of going to Mobile 1, 15W50 oil, instead of Mercruiser 25W40 stock oil. I was looking for any input/advise if this was the correct weight and viscosity oil to use or not. Any expertise on this?
Thanks, InXS

I don't know either but I just bought the same oil for my 02 575 with 100 hrs. Have been running kendall 20-50 dino juice. Trying to decide also whether to put the Mobil 1 in over the Kendall.

15-50 Mobil 1 will be fine.

If you're not running thermostats, 0-40 Mobil 1 is a good choice.

If you want a real good oil to run Royal Purple Racing 51.
It is an oil design for extended periods under extreme pressure and heat.
A little $$ but worth it if you are looking for a real good oil.
It's viscosity is typical of a 20W/50.

RoyalPurple Racing 51 ,yep,thats the one.I ran it in my 2001 HP500 for 280 hrs & I'm going to run it in my new 540.BOB