Hey all , new to this forum. I hope i am clear with this situation. I work for a rebuilder who recently sold a split seal Marine 454 engine. On startup the engine shakes dang near out of the boat. I never had this customers flywheel, so i used a master flywheel i had to balance (454), and a brand new dampner also for a 454. We hot ran the engine an it performed beautiful.
We took the master flywheel off, and sent the engine to the customer... the customer installed and started it and all hell broke loose. I know that the 454 is externally balanced and vice versa...but does anyone know a distinct difference between the 454 or the 427 flywheel.

Thanks in Advance

Justin