1987 Four Winns with 4.3 Merc. Engine Clacking
The motor purrs beautifully when running at lower rpms. but as soon as you plane out putting a load on the engine,it starts to clack, as though one lifter is not getting enough oil. It seems to have lots of power still.
I have tried putting Sea Foam in the oil and running it for a while. Then changed oil with new. I always change the oil every year.