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ContinuousWave: Small Boat Electrical
Wiring of Evinrude Alarm
|Author||Topic: Wiring of Evinrude Alarm|
posted 05-03-2010 09:58 PM ET (US)
The [alarm] buzzer [on an Evirndue 90-HP] has a black wire that is about an inch long and not connected to anything. Is this right?
I have a 1982 17'Montauk with a 90-HP Evinrude. I am having trouble with my warning buzzer. It doesn't give me a test beep when I turn on the key and when it does make a sound it won't shut off and sounds muffled. I have purchased a replacement which should be here in a couple days, but I am curious about the wiring.
posted 05-03-2010 10:08 PM ET (US)
The wiring is shown in the OEM Service Manual.
posted 05-03-2010 10:15 PM ET (US)
Evinrude alarm wiring also shown here:
Generally a wire is not left floating in air.
posted 05-04-2010 04:08 PM ET (US)
Thanks for the reply, but I figured it out. I [knew] [the wire from the alarm buzzer with black insulation that was not connected to anything] had to be ground, but when I grounded [the black wire] the buzzer wouldn't shut off. I did some more investigating and found that when the previous owner eliminated the VRO system they didn't unplug the VRO wires on the fuel pump. I hooked up the ground on the buzzer and unplugged those wires and it works perfectly now.
posted 05-04-2010 10:27 PM ET (US)
I don't know exactly what you mean by "the VRO wires on the fuel pump." THe VRO system is described in detail in another excellent article in the REFERENCE section. Please see
Typically the VRO pump has just a single wire output that is associated with the alarm system. The wire is typically a tan wire or a tan wire with a yellow stripe or tracer, depending on the generation of the fuel pump. In the pre-c.1994 OMC outboard, prior to the System Check wiring era, there is just a tan wire. In later motors the wire tan from the fuel pump that is sent to the alarm may have a yellow tracer.
The purpose of this wire is to signal an alarm if the there is no oil being pumped. The alarm signal is developed by electronics that are internal to the fuel pump. The fuel pump is supplied with ignition pulses so that it has a sense of the engine speed, and it looks for pressure pulses from the oil side of the fuel pump in corresponding ratio to the engine speed. If there are not enough oil pressure pulses to correspond to the engine speed, an alarm signal is generated.
The other wires on the pump, which in the modern versions of the OMC oil system is called the oil mixing system or OMS pump, are to supply battery voltage to the circuitry and to supply the ignition pulses to cue the electronics on the engine speed. Perhaps you were referring to these circuits as "the VRO wires."
The alarm system of the OMS pump is described in detail in another article,
in the subheading Alarm Sensors and System.
If your OMC motor has had the OMS or VRO pump removed, that is a shame, as they are excellent oil mixing systems. You will be left with just the over-heat alarm.
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