I’m hoping to get some information. I have a problem I have not run into before.
I have a 1999 454 Mag MPI with 50 hours on it. It is stock with the exception of recently added Stainless Marine Exhaust. The last time I ran the boat prior to adding the SM headers I had white smoke or steam coming out of the starboard bank exhaust. I idled back to the ramp and put it up. I made some calls and consensus was a bad exhaust gasket. Or hopefully so. I had new headers coming in so I waited. I pulled and replaced the plugs. The plugs were crunchy plugs with deposits on them. OK, maybe I got some bad gas and it was from sitting up over the winter. I topped off with premium and added dry gas.
After installing the new headers (a two hour job), replacing the gimbal bearing and aligning the motor I went to run it. Now I have what seems to be a backfire in the starboard side. It runs smooth for a few seconds and then pop, smooth then pop and repeat. I ran it for about two minutes to see if it would clear but no.
If anyone has any ideas, I would greatly appreciate the help.
Thanks,
Taz