[C320-list] Transmission lubricant

[Jeff Hare]

Graeme, 

I changed ours the first year we got the boat (new).  Checked it from that
point on and really didn't change it for 6 years.  When I drained it out, it
was indistinguishable from the brand new oil I was putting back in.  Clean,
slippery with no hint of grit.  I've never had to add a drop between
changes.  I'd guess the only concern about overfilling would be foaming.
Under filling might result in the gears not dipping in the oil.?

All that said, our boat is 19yrs old, ~650hrs and it's been "changed" 4
times but never once looked dirty. It's important that it not run low or be
over filled and our local yanmar guy said it won't take the full amount on a
change (as others said) because of the angle the engine is sitting at.

Side Note:
The exact same thing can be said for the Yanmar. It's not quite like a car
where you have a High and Low level.  With the g3m, you ideally want it
right at the full line when the boat is sitting at the dock, not over or
under.  That way, you get the splash lubrication, pumped lubrication and
drip lubrication systems all working optimally when (gasp) motoring or
motor-sailing (which of course none of us ever do, because it's a sailboat,
right?).  

If you're near the low line, and heeled at all, then you may be losing some
of the effectiveness of the splash lubrication that takes care of the
underside of the cylinder walls, even though the pump is still doing its job
properly.  I'm not a marine diesel mechanic so this is probably
over-simplification or only partially correct.  When I took a Marine Diesel
class, this was something that they harped on quite a bit.  They said if you
over fill the engine and heel the boat, excessive oil could result in diesel
runaway in some extreme case. I'm not sure there's any PCV system in a
marine diesel, so maybe excess foaming would increase crank case pressure
and cause oil to work itself into the cylinders and burn along with the
fuel.  Anyway, it can't be a major a point of concern since I've really
never heard of it happening, but just know it could if the conditions were
right.?

-Jeff Hare
2001 #809 Woodbine II

-----Original Message-----
From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf Of
Graeme Clark
Sent: Thursday, August 6, 2020 4:40 PM
To: Catalina list <C320-List at Catalina320.com>
Subject: [C320-list] Transmission lubricant

A couple of questions
1) How quickly does the fluid deplete? How often should I expect to top it
up?
2) What is correct fluid? I assumed automatic transmission fluid but reading
the manual (engine is 3GM30F) I suspect it might be ordinary engine oil?

Thanks
Graeme
1996 #366, UK 


Sent from my phone. Excuse typos!