I have a 1977 24 foot FiberForm with twin 140 Mercruiser I/O's. The problem is one is starting and the other is not. It appeared to be seized but after much effort, I got it cranking again. When I was working on it, I pulled the distributor. Now when I turn it over, it backfires up through the carb. I brought the timing mark on the crank pulley (it was never removed) around to the tab on both motors. The rotors on both distributors are pointing in the exact same direction. Both motors have been converted to electronic ignition. I can't help but thinking I didn't install the distributor correctly, but everything seems to be in the right place. I'm stumped. Any help at all would be awesome, Thanks