" Chris.... The ratings of oct
" Chris.... The ratings of octane may be different where you are, but in the states unleaded 87 octane is recommended. Any unleaded above 87 octane is fine but choose the lowest rating above 87 if the 87 octane is not available.
The 1968 5hp was manufactured after OMC came out with the 50/1 oil and they (OMC) published a bulletin which stated that "all" of their engines could use this (50/1) mixture excepting the 1957 7.5hp (I have no idea why the 7.5hp was excluded).
Bottom line is that you can use the 50/1 mixture (1pt 50/1 oil to 6gal gas) but use only the 50/1 oil that is marked TCW-III. I prefer the OMC or Mercury Quicksilver oil, but that choice is yours.
Some will argue that your engine should use the 24/1 mixture (1qt of 50/1 oil to 6gal gas) due to the fact that the engine does not have all roller/needle bearings.
Frankly, I have some reservations about that argument due to the crankshaft bearings being what appears to be a bronze type material instead of a roller or needle bearing. However, OMC did make that statement in their bulletin and there are many small horsepower engines with those same type bearings still running strong which are using the 50/1 mixture. Sort of proves OMC's statement.
The OMC part number for the propeller is 380104 but it has been unavailable since 1984. It's possible that some dealers may still have one in stock though, and I'm sure that there must be many other companies that still manufacturer them.
Joe (30+ Years With OMC) "
