SB

iTrader: (1)

No.
(Not even Mercruiser)

TomZ

iTrader: (2)

Merc 500 EFI oil viscosity chart from the manual:

Ryan00TJ

iTrader: (8)

Unlimited jd

iTrader: (5)

With as tight as the rest of your engine is, I’d want to know what the bearing clearances were before deciding which oil viscosity to use.

PQ290Enticer

Mains are .0025 on one and the rods are .0035. The other engine Mains are .0027 and the rods are .0025. My builder didn't say to run 10w30 when installed in the boat. He just used it for the dyno runs. Maybe this is what he's thinking. I will be meeting him next week and will ask what his thoughts are. I've been told that I could run the 20w50 if I wanted to, it would raise the pressure(?) but not to a level that may hurt the filter? Again, an exploding oil filter is something that never occurred to me.

TomZ

iTrader: (2)

.0035 on the rods? Are you sure that isn’t a typo?

PQ290Enticer

Not on my end. Funny enough, that engine ran just slightly better than the other.

boostbros

we run shell rottella 15-40 in all engines not supercharged and mobile one 20-50 V twin in those have dissasembled a few and they are clean and bearings look good so we stick with what works

snapmorgan

iTrader: (2)

Where is Borgie when you need him? Oh yeah, he got banned.
I personally have had very good luck with 15-40 Rotella and Valvoline VR1 20W50
I wouldn't use Mobil 1 of any viscosity

DrFeelgood

do you run conventional Rotella or synthetic Rotella?