Timmer1973
New member
I have a 1999 4.3 Alpha 1 stern drive that has a knocking sound when running and not in gear. It gets louder when the leg is trimmed up or the steering is turned. The sound corresponds to the speed of the engine and doesn’t go away when in gear. I had it in the shop and got the gimble bearing replaced (so they say). I thought it was the u-joints but they both look brand new and zero play. I have had both manifolds off and cleaned them out and both flapper valves are in place and look new. Anyone have any ideas what the knocking could be? It has gotten louder since last year.
