Looking through an actual 1975 Johnson service manual for models 4w75 and 4r75, not a Clymer or Solec aftermarket manual. In 1975 Johnson recommended either OMC Sea-Lube Premium Blend Gearcase Lube or GM Dexron transmission fluid. I've been using Citco 90 weight marine gear lube. Obviously a thicker lube than what was originally called for. Could this be the reason my seals suddenly failed? Just got the manual in the mail today ( got it off e-bay). Other than very old outboards calling for grease and certain electric shift outboards needing special gear lubes, I've never seen a manufacturer calling for anything but 90 weight marine gear lube. For those of you that have 1970's 4hp OMC's, what lower unit lube are you using?
