Older Mercury Oil/Temp alarm

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David R

Seaman
Joined
Aug 21, 2001
Messages
61
I have a 1987 70hp Mercury with a Quicksilver control. The problem is with the alarm giving false warnings. When the key is in the run position the alarm sounds and won't stop. Start the engine and the alarm may go away or go into this annoying fading off and on mode, mostly on. I've checked the temp sensor, no continuity to ground. Oil low sensor no continuity between leads. Disconnected both, also doesn't stop the alarm. I should replace the module at this point, but I'm confused by one other issue. When I disconnect the purple wire to the alarm module, the tachometer acts up. It may or may not work and jumps around erratically. Sometimes if everything is hooked up, it sounds like an arcing sound or snapping sound coming from the control assembly as the horn activiates. This sound is quiet plentiful when the engine is cold and missing, the tach jumps all over the place. I don't believe the high-voltage is going through the controls, because all the weird symptoms go away when the purple wire is disconnected.<br /><br />Ok so two questions.<br /><br />What does the alarm circuit have to do with the tachometer circuit?<br /><br />The alarm horn is in the controls box, how is it wired in?<br /><br />My Seloc manual doesn't show either of the circuits in a completed fashion.
 
D

David R

Seaman
Joined
Aug 21, 2001
Messages
61
Re: Older Mercury Oil/Temp alarm

Does anyone have a complete schematic of the controls (including alarm) wiring that they could email me?
 
D

David R

Seaman
Joined
Aug 21, 2001
Messages
61
Re: Older Mercury Oil/Temp alarm

Yeah you're right that wasn't the best way to put it, I was thinking of more of my local boating area. The change over to new 4 strokes is full steam ahead. Making me the old guy.<br /><br />Haven't had any luck with the link. The fellow who runs the site is out for heart surgery<br /><br />Any other sites? This is something I need to look after. If the grounding route is the issue it could eventually stop the engine from running.<br /><br />David R
 
G

gss036

Commander
Joined
Jan 18, 2003
Messages
2,914
Re: Older Mercury Oil/Temp alarm

Not familiar with your motor, but in general terms, the purple wire is normally a power wire and is used to jump power from one instrument to another. The alarm circuits are normally brown or brown/blue. Constant beeeeeeeeep is usually the over heat side of the system, beep, beep etc is the oil side. Does your oil tank have an oil level indicator? Is there an oil pump indicator. I think with what you are describing, I would check all the black ground wire to make sure you have not lost ground somewhere. Not much help, but something to think about.
 
D

David R

Seaman
Joined
Aug 21, 2001
Messages
61
Re: Older Mercury Oil/Temp alarm

This past weekend I dismantled the controls to trouble shoot, as nothing would happen at all. Was getting only ~6.5 volts on the Red wire, main supply. Traced it back to the in-line fuse holder, just making poor contact on the fuse. So I pried the internal contacts for better fit. That took care of the no action at all.<br /><br />The Purple wire is 12 volt supply out of the ignition switch, only getting 11.5 out 12.8 volts. Moved the horn to the dash board wiring, so that I can disconnect if it acts up. The Tan/Blue from the alarm circuit mates with a Tan wire on the horn and feeds. This wire could also be light-brown/blue. The horn also has a Purple wire which connects to the Purple wire out of the ignition switch. Another purple wire feeds power to the Tach in the Dash. After dismantling and re-assembly everything worked properly. Unfortunately a day later it didn't, but only had to pull one wire under the Dash.<br /><br />I'm currently trying get an old control box to cannibalize for the ignition switch. This seems like a good choice as sometimes the Tach goes weird with the needle flying around, or not moving. The reduced voltage may be also be triggering the alarm. The overheat sensor, and the low oil sensor both check out fine.<br /><br />David R
 
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