just intalled a new/rebuilt 4.3 v6 i/o mercruiser in my 92 bayliner. the block came with the heads installed. both exhaust manifolds are new. engine runs great and idle is real smooth. however, i'm hearing a loud bang noise which to me sounds like a piston hitting the valve only when exceeding 3500 - 4000 rpms. noise is not constant it comes and goes. under 3k rpms all is smooth. the only thing not new on the boat it the intake manifold and the drive of course. any input or advice would be greatly appreciated.
