Marelon Valves
I Second the get rid of the Marelon Valves.......you never know what will jam them up, and when they will jam up.....
Replaced mine with Groco Bronze and they work beautifully.....so far no need to service them with the boat in fresh water and relatively far away from both natures fallout, and industrial fallout.....two years and counting....
Not cheap, and a lot of really cramped body numbing work.....had a friend do it for me, but I did help, and it was painful.....
My $0.02 worth