I designed this for my 1957 5.5 hp johnson outboard. since the standard headphones for cooling will not fit these older motors. It allows you to connect your garden hose to your motor for cooling. I used a Gardena coupling as reference but many more types will probably fit.
It'll probably fit many more models every OMC between 5 and 25 hp up to 1970 will probably work.
I used 50% to be sure its watertight.