i operate a 1989 searay with a 454 mercruiser engine and bravo one outdrive.i recently replaced the engine with a new long block,which now has 15 hrs of breakin time.i also learned during swapping parts from the blown engine to the new block that the blown engine was a 1998 rebuilt.during the 15 hrs of breakin,the boat had a moderate vibration at all rpms.could installing the 1998 harmonic balancer onto the 1989 long block cause the vibration,considering coupler,outdrive,gimbal bearing,alignment check ok?
