I'd listen and go 40.... particularly if it's got some hours on it.

-W (runs 20/50 in the '68 Vette with a zillion miles)

"WaIIy" wrote in message
...

I have Mercruiser 5.7's 1989 and boat on Lake Erie near Cleveland.
My mechanic recommends straight 30wt oil and that's been fine, today he
said a new bulletin came out from Mercury and it was something like 30
wt up to 60 degrees F and 40 wt for over 60 degrees F.

Now my mechanic says to use straight 40 weight.

What do you think?