You don't need to pierce the wire in there. You slide your pick in-between the wire and the wire cover until you hit the metal connector.
I would think the sensor would ground out internally not in the body of the sensor but I could be wrong.
Did you check both sensors?
I believe your incorrect. Same block and it's the newer style with the round plastic access covers with a o-ring. Other style is at the back near the bottom of the engine.
Shove a metal pick down into the tan wire under the clear or black rubber cover coming from head sensor. Ground it to a head bolt and see if your alarm goes off.
I'm betting your sensors are bad because your temp readings are to hot.
The orientation is a no brainer on this....shows it clearly...
Can't really answer your question but if you're running that hot and your alarm is not going off you have something wrong and the alarm system. Is the control box horn giving you one beep at startup? Otherwise test the sensor on the heads.... Easy to do.
I'm surprised you can keep your finger...
Yeah, seems sketchy.
Post your model number so we know what you have. Any videos of it running? YouTube's are easy to make and send.
What other diagnostics were done?
What part are you referring to....
https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1972&hp=25&model=25RL72R&manufacturer=Johnson§ion=EXHAUST+HOUSING
