Greg wrote:
because 30w does not lube pressure oil bearings as quickly upon engine
startup
as does 5w-40. Not by a long shot. you can hear the difference, easily.


My point is Merc says to use 10w-30 OR 25W-40. (the only grades they sell)
30HD seems to be right in the middle.
Merc doesn't make 30HD and I suspect that has more to do with the recomendation
than anything.
I do know their 10W-30 is breaking down after 20 hours and I am losing oil
pressure. That is not a good thing.

Before you ask, no they don't have any answers ... I asked.

I still wonder if my Atomic-2 engine would work better, or longer,
if the recommended 10w oil was replaced by 10-30?

My oil pressure goes from 20# cold to 7 or 8 when warmed up to the
"warm" range. I have no thermostat, so the engine is always working
'cool.' Plugs carbon up, I don't care, they are still cheaper than
gas and easily replaced, but my valve guides, piston tops, etc, are
all black, I suspect.

All I want is to get to and from a mooring with reliable backup if
the sailing or current puts me onto the nearby rocks, and the
occasional one day voyage sometimes under power as the times
require, to and from the cottage and the ramp.

Terry K