Oil Question???
 

I have a 2001 Fastech 312 with twin 6.2 MPI 320 hp motors & mostly run it at LOTO where water is 80 deg & air is that or more. We run at 3500-5000 Rs all day.
I bought the boat last summer & couldn't get the previous oil being used. When I changed the oil I put Merc 25/40 in them, but my oil pressure was not the same after motors warmed up as before the oil changes. So I'm thinking of going with Mobil 1 15/50 & hoping I'm good after that. What's your opinions of me running 15/50 in 377s & what filter would you all recommend?
Motors have around 250 hrs.
Thanks

Mobil 1 15w-50 will be great. Be Happy. :)

What's the best & biggest filter I can run?
With the small oil pan I want to run the biggest filter I can...
More oil the better!
Thanks

Whats the part number on your current filter?

Mobil 1 15w-50 is all I have ran for about the last 1000 hrs on 3 different boats.
I run the Mobil 1 M1-302 filters. They are the same size as Merc filters but filter better and flow more..

But, I think differently... if the biggest filter holds 1qt vs 1/2qt of smaller filter that's less oil in the pan when running?
Loving oil threads...

I've been running Amsoil 15w50 racing oil with a Donaldson P550832. I run pretty hard for long periods of time with an oil cooler that's smaller than it should be, my oil can sit at 280+ for 30 minutes while I run across Lake Huron. No oil breakdown, no change in pressure from old to new. I've done tear downs just to see how my motor is doing and it still looks like new, no varnish or sludge. Bob Teague ran Amsoil racing oil all season in his race boat with no measurable wear after a full season of racing. FWIW

The M1-302 filter number is now M1-302A after checking today.