Ok I was reading through the Marine engine section of BITOG, and I never thought before that Marine use could be so much harder on an engine than on land. I figured the running at constant RPMs would be easier on it, but apparently not. Ok, so let me get a few things out of the way that I think I know. 1. Marine engines run very rich, cold and wet. a. Dunno why they run rich---? b. They run cold for best power output c. Wet because of close proximity to water 2. Have very high shearing affects... Why exactly? Course it might be good to know what shearing means, so a one sentence explanation might help with that one too. So why else is marine use so [censored] hard on engines? Truly, I don't know. I hope y'all can explain it to me pretty good. Also, years ago we rented a 21' Bayliner Ski-boat, with a 120HP Mercury Marine Outboard 2-stroke. Would that have been a 3, 4 or a 6 cylinder? Thanks in advance!