I have an 02 342 with twin 6.2 engines. This past summer I noticed the engines were continuing to run rich after they warmed up. Mostly because of the rich smoke. My mechanic has been working to fix it this winter and has replaced every sensor associated with the ECM, had the injectors checked and cleaned, fuel pressure is 25 psi at the rail, and it is still running rich. Have you had this issue with 6.2's? My mechanic is in contact with Mercruiser and they are leaning toward an intake gasket leak or internal vacuum leak? Any ideas?