I have an '81 Johnson 50 that I primarily use in freshwater but lately I have wanted to use it in saltwater enviroments. I see that on later model outboards they have factory installed zincs bolted to their lower units to help combat corrosion. Does my outboard have a factory installed zinc that I do not see? I know I need to have a zinc to protect my engine, but where would one be located or where should one (or two) be installed. This forum has been very helpful to me in the past and I really appreciate it. <br /><br /> Todd Tedder