The Cole Hersee Marine engine kit is the most simple I've seen yet.
(In Aftermarket offerings) (Even with it's super low OP threshold)
[Cole-Hersee (COLE # M-40177-BP) ]
It Encompasses BOTH High Temperature and Low Oil Pressure with an Audible
Alarm.

Yanmar uses the same Dual Alarm type on some of it's smaller Marine Diesels...
I'll call the distributor's service people maybe this coming Monday.

Hell, some mornings a Buzzer screaming during the "Glow" would serve to Keep
You Awake long enough to start the engine.

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'84 300SD sold
124.128