This is what I think happened based on what I see in the manuals and previous explanations (from Frank R. I think)
They started out with a single thick gasket, then “OMC came out with a baffle kit (and 2 thin gaskets) to shield the crankshaft area from the exhaust and water/steam on the troublesome motors. It did very little good.”
By 1968 they started using a spacer (18-20 HP) to isolate the driveshaft and seal to basically attempt to do the same thing. At that time they went back to using a single thicker gasket and no baffle.
