Originally Posted by LakeSuperiorGeezer
I rebuilt a 1972 Ford 302 used in a one ton van with an RV built on it. The engine had sodium filled valves from the factory, but no hard seats. The amount of valve seat erosion made me wonder if the heads could be salvaged. Not a problem. It looked worse than it was and the new hard seats fit just fine. All of the sodium filled valves were reground and reused. Unleaded gasoline came out several years later. It must have taken at least ten years for the problem to develop. In a boat it might happen sooner since a lot of operators run boat engines at wide open throttle.
It would appear that short of up grading the valve system the advice of MMO & lead additives may be about all one can do? If it runs well, maybe take a compression test once in a while, change oil often and hope for the best. It was my experience that valve related problems come on somewhat gradually so it shouldn't just quit running all of the sudden?