Thanks for the feedback guys. Reason I'm asking is because the owner's manual doesn't specify any brand let alone Yamaha's. It calls for a "90 weight hypoid oil" and I have several quarts of OMC's ultra HPF oil already.
I am with Ray, wont hurt anything.
in fact I have a few customers that wont do regular service that I run the volvo synthetic GL-5 stuff in at about 12 dollars a quart
While the owner's manual lists the type of oil I have noticed that the Yamaha factory service manuals gives the specific part number for the preferred oil. No surprise that it is Yamaha oil. Yamaha does claim that their oil has corrosion and rust inibitors.