Hi there all, I have a Mercruiser 5.7 and what I thought would be an easy spark plug replacement has turned into an absolute nightmare. I'm an experienced auto mechanic but don't have quite as much experience in marine engines. I went into the job thinking it would be the same as replacing the plugs on a typical GM 5.7 but had no idea the incredible stupidity of Mercury engineers. I got plugs 2,4, and 8 out fairly "easily" without much hassle, but plug #6 under the exhaust manifold has put me in quite the bind. All the plugs on the engine were severely corroded and took a bit of force to get them out, but I didn't realize my thin wall spark plug socket had gone at a slight angle when trying to take #6 out, the socket had come into contact with the exhaust manifold and had angled just slightly, I didn't notice as first thinking it was just seized badly like the others, by the time I realized what had happened I stopped immediately. The spark plug is still in there, but I'm thinking I've stripped at least a few threads either on the plug itself or the head. At this point, I can still apply a considerable amount of force and the spark plug seems to be coming out, but I don't want to risk further damage if possible. So my question is what is the best course of action at this point?
1) Keep loosening the spark plug and hope it comes out, then assess the damage and decide what to do
2) Remove the exhaust manifold entirely which is a royal pain in the ass on a 1997 Bayliner Capri, there is no room at all to work with, that engine bay was really designed for the 3.0L I4, not a 5.7 V8. And even after removal, I'm not sure it would help me much to straighten the plug out in this situation?
3) Completely removal of the head? Obviously an absolute last resort, but if need be I can do it.
4) Other ideas??
1) Keep loosening the spark plug and hope it comes out, then assess the damage and decide what to do
2) Remove the exhaust manifold entirely which is a royal pain in the ass on a 1997 Bayliner Capri, there is no room at all to work with, that engine bay was really designed for the 3.0L I4, not a 5.7 V8. And even after removal, I'm not sure it would help me much to straighten the plug out in this situation?
3) Completely removal of the head? Obviously an absolute last resort, but if need be I can do it.
4) Other ideas??
