Check your exhaust manifold. I had similar issues and the manifold had an internal crack.
I have a Jefferson 42 also and in reference to the difficult steering issue, mine had the same problem. The boat had sat for a long time and the rudder shafts’ grease had hardened. I pumped new grease into the zerks and it freed up the steering.
Just looking at the pump condition, you may need to have them rebuilt.
Thanks. That’s about what I guessed. Time to upgrade.