Hi!

I honestly can't answer that definitively, but I can tell you that lower
unit design goes back to 1962 before a lot of fancy lubes were available at
all, so my instinct would be yes.

That said - I use the Mercury brand lube in mine, it's not so expensive as
to not use it.


Now,

While your paying attention here's a bunch of free advice. Make sure your
timing at *max* advance is set to no more than 21 degrees, that you use a
good mid-grade gas, and that it's propped to make at least 5500 WOT. Those
motors are known for being a little "piston happy" and the above precautions
will keep your powerhead happy.

Use a can of Mercury "Power Tune" as directed once a year. Those motors that
havn't popped a piston (and therefore seen an overhaul) have a LOT of
"coking" going on around the rings from all the years of use. Stuck rings
are the *second* most common cause of failure of those powerheads.
Using a good quality ashless TCW-3 helps a lot in this area. I use the
Pennzoil Synthetic Blend - It's only $9 a gallon at Wal-Mart - great stuff!

And lastly make sure your carbs stay clean and your fuel pump stays in good
shape, you don't want that critter running lean.

-W





"Blorf" wrote in message
...
Hello,

Can I use type 'C' 90 weight lower unit oil in a 78 115 Merc? I can't
seem
to find the 90EP readily. Is the type 'C' an 'EP' with more additives?

Thanks.