Alarm

sogood

Petty Officer 1st Class
Joined
May 11, 2016
Messages
361
I've seen mention in various posts about an alarm fitted to the engine, to warn against low oil pressure/ overheating. From what I've seen in my refurb, I don't think my 1990 mercruiser 5.7 is fitted with any such alarm. If it is, where would it be and if not, is it possible to retrofit such a system. I imagine it wouldn't be too complicated and would like to have the extra safeguard. Thanks in advance.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,398
The alarm (buzzer or horn type) would be mounted under the helm. The key supplies power to all systems when key is turn to ON via the purple wire. The purple wire coming from the key switched is daisy chained to all gauges and the alarm. On the other side of the alarm is a Tan/Blue wire which goes back to the motor via pin number 4 on the 10 pin harness connector

Harness Connector.jpg

Once on the motor, the Tan/Blue wire goes to one side each the, drive lube bottle, temperature switch, and oil pressure switch. The other side of these thre switches goes to ground. The lube bottle is the only one which is grounded thru another wire coming off the bottle, the rest are screwed into oil ports and thermostat housing.
 
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