What is the correct fuel/oil mixture for my outbaord boat engine?

What should i be mixing my fuel at for my 2003 90HP Johnston engine? the guy i bought it from had said something like 50:1. I just want to see if anyone else has advice. Thanks. Also the decals on the engine were removed before i bought it so im unsure if it is a saltwater series engine, but doest sacrificial anodes usually mean its saltwater motor?