The 3 gallon tank Frank mentioned is not a pressure tank per the title of your post. OMC used pressure tanks on some models through 1959. The 4 and 6 gallon ones were used from the mid 1950s through 1959. 6 gallon tanks from 1957 up had a plastic primer button instead of metal. I’ve never heard of a 5 gallon pressure tank. Was the 5 gallon the earliest tank that was shaped a bit different? or an aftermarket tank?
Dave
