Doobie wrote in message . 95.104...
Im due for an oil change for my boat and im wondering what the concensus
is on Synthetic oil vs. Mercruiser brand for a 7.4 liter (454ci) 1988
engine.
Is it worth the extra $$$?

RK
27' Sunrunner
Lake Simcoe
Ontario,Canada

Very Interesting question! I installed twin Mercruiser 350s (and Bravo
III outdrives) in May 2000. When oil change time came around, I bought
Mobil One oil. A yachting buddy recommended it and I was "going to do
it right." I just happened to read the Operation and Maintenance
Manual one last time before beginning. In the 2000 manual, page 77, it
says, in big bold type, "IMPORTANT: The use of non-detergent oils,
multi-viscosity oils (other than Quicksilver 25W-40 or a good quality
20W-40 or 20W-50), synthetic oils, low quiality oils or oils that
contain solid additives are specifically not recommended."

I called another buddy, who has an 1986 Mercruiser 350 (and manual).
His manual is identical except that the phrase "synethetic oils" is
not there. I interpret this to mean that Mercury has, somewhere
between 1986 and 2000, specifically added a recommendation against
synthetic oils.

I took all the Mobil One back, bought the Quicksilver Oil (its
available within walking distance of my slip and is not excessively
expensive) and change the oil and filter every 100 hours or less. Like
the book says.

FWIW