Originally Posted by keeno07
I have a Mariner 30M, 30hp 2 stroke. I have been told that I do not actually need marine 2 stroke oil & that normal 2 stroke oil is good enough. Does anyone know if this is correct?
Absolute b%ll%cks - a prime example of why you should always follow the guidance given in an engines owners manual in relation to oils etc - they are the expert not a mate or someone in a bar.
TCW means "Two Cycle Water-cooled" -- any other oil will most likely be formulated for air-cooled engines which typically have higher combustion temps. A water-cooled outboard does not generate the heat required to burn off all ordinary 2 stroke oil - especially if you aren't running at WOT most of the time.
Excess unburned oil means more and faster carbon build-up on cylinder walls, piston crowns and transfer ports. Coked-up cylinders lead to sticky rings, losted compression and therefore lost of power and maybe engine failure.