With all of the activity aboard a sailboat, it is very easy to miss the fact that your engine is in trouble. A complete and functioning alarm system is the only thing between your engine and a dangerous and potentially very expensive engine failure!
Early engine installations were missing a high temperature alarm. Even when there was a buzzer, it only warned of low oil pressure, not high temperature.
Temperature alarm on early boats
This is potentially a very expensive omission. Water pump impellers fail regularly. A high temperature alarm is the only warning you will have that your impeller has failed and your engine is overheating. It is very unlikely you will notice the temperature gauge indicates high engine temperature before the engine seizes.
They used a printed circuit board with built in logic to cause an alarm to sound at the appropriate time using only the engine's temperature sender and oil pressure sender. In theory there was no need for a separate temperature switch to activate the high temp alarm. The circuit board was designed to sound an alarm when it sensed the correct resistance through the single temperature gauge sender. The company that made the printed circuit board is no longer with us...probably because the failure rate was so high.
By replacing the thermostat housing and thereby adding the high temperature switch, you can add an alarm even to those boats that had no temperature alarm at all.
Adding a margin of safety to earlier engines
Most engines including those used in in the 1990 and 1991 boats (and earlier) can be retrofitted with the newer alarm module. This will provide a low oil pressure warning as well as a high water temperature warning. To retrofit your engine, call our tech support line. Choose kit #Z2754 if you have an M2-12 or M-30. If yours is an M-18, M-25, M-25XP, or M-35 use kit #Z2753. For the M3-20 use our kit Z3536. See note 2 below if you have the early 5411 engine.
1) An alarm should sound as soon as your ignition is switched on. In fact, it should sound any time the ignition is switched on but the engine is not running. If this is not the case, investigate immediately as you do not have the protection of a low oil pressure alarm.
2) Universal never provided an upgrade to add a temperature switch to the early 5411 engines, so we do not have a ready-made solution for that engine.