Roger what is the temp half way up? My normal reading is slightly over half way but thatís 175 while my actual temp is ~160 which would b3 half way. Wiggling wire is not a good troubleshooting technique, remove the wire and clean its connection and reinstall. Mercruiser uses a t-stat gasket with brass eyelets to provide a ground and these become problematic.
Through away that manual and get the real Mercruiser manual under Documents of this site.
1997 2400 SCR
5.7 Vortec / Bravo 2