While troubleshooting non working temp gauge, using my IR Gun, getting 140 temp at temp sender, 90 on risers, 150 on heads, however the intake water crossover that the thermo housing bolts to about 200. This is idling after a brief run at 3500 rpm.

Is that normal? This is an Edelbrock AirGap on a 489 Merc.

I would think the bolts are maintaining heat because they are in the block but your 140 may be alittle low. 160 ish would be nice. Depends on water temp coming in and the thermastat 90 and 150 sound good. Do you have a oil temp gauge?