1980 mercruiser 5.7

yimmyb

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Feb 22, 2017
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Received boat back from shop after having minor work done. Now motor turns over just fine but when key is put back to run position the boat quits. Noticed a red and blue wire coming from the key switch that is not connected to anything. I believe it may be the accessory wire.
​Could this be my problem and if so where does it connect?
 

Baylinerchuck

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What was the minor work you had done? Any chance the "shop" may be responsible and should make repairs?
 

Bt Doctur

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!980`s didnt have an accessory position just off-on-start , what work was done?
 

yimmyb

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Feb 22, 2017
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Could it be something in the starting/ run wiring system? I also found a large orange wire coming from the alternator running up to the dash that is not connected. Is this for the voltmeter? The boat is a 1980 Searay 210 cc with the 260 horse 5.7. The closest wiring diagram I can find is for a 1984 boat of same style. I also have a Selok book on the boat. I am still unable to find an ignition wiring diagram that shows the wiring for the key switch. Any ideas?
 

Bondo

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Ayuh,..... Welcome Aboard,.... With a test light, test the wires at the switch,...

Batt, oughta be a red wire that's hot all the time,....
Start, oughta be a yellow/ red wire, hot only with the key in the start position,....
Ign. oughta be a purple wire that's hot in the start, 'n On positions,...
 

wrench 3

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Aug 12, 2012
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From you description of the orange wire it sounds like it was wired for an ammeter. Your engine wiring is on page 402 at http://boatinfo.no/lib/mercruiser/manuals/mercruiser3.html#/402 your instrument wiring is on page 430.
If you take a look at the engine wiring you will see that the starter system hot wires the ignition when the starter is engaged. However it appears that the purple wire isn't supplying juice to the ignition once the starter disengages. It may help you to find out if you have 12V on the purple wire at the alternator when the key is on.
 

yimmyb

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Feb 22, 2017
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Is this with engine running or just key in run position? With just key in run position all checks on the ignition key switch are fine, but no voltage on purple wire on alternator
 

Bt Doctur

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Does the purple wire sat the switch have 12v in the run position No, check red wire, replace switch
Yes, go to engine side of harness plug, locate purple wire at the electric choke , or alternator check for 12V, if yes go to + side of coil and check for 12v .
If No, resistance wire went bad
 

Rick Stephens

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Does the purple wire sat the switch have 12v in the run position No, check red wire, replace switch
Yes, go to engine side of harness plug, locate purple wire at the electric choke , or alternator check for 12V, if yes go to + side of coil and check for 12v .
If No, resistance wire went bad

Zactly!
 

wrench 3

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Is this with engine running or just key in run position? With just key in run position all checks on the ignition key switch are fine, but no voltage on purple wire on alternator

There should be voltage on the purple at the alternator with the key on and the engine off. Since you don't have any there's a brake in the circuit between the key switch and the engine.
To start off inspect the harness plug between the engine and remote harnesses damaged or pushed out connectors. Also inspect all the purple wiring and the harnesses for physical damage.
I just remembered that you said that you had work done on the gauges. On the wiring diagrams that I sent you the link for it shows the purple wire going from the key switch to the tack and then from there to the rest of the system. This may be a good place to start. Maybe they forgot to reconnect something.
 

yimmyb

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Feb 22, 2017
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Thank you to all for the information. I found a purple wire from the alternator that was not connected. The boat now starts and runs. My next problem is my alternator is putting out 28 volts and the batteries are not being charged. I disconnected the orange wire from the alternator as to not damage any circuits. Thoughts? The alternator was recently replaced with a match from the alternator that was installed.
 

wrench 3

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In post #6 you mentioned that the large orange wire from the alternator was not connected under the dash. That is the wire that connects the alternator to the battery. If the ammeter was replaced with a voltmeter, the two orange wires and the red/purple wire from the ammeter should have been connected together but not connected to anything else. It sounds like they joined the small orange wire and the red/purple wire together but left out the large orange.
You need to find where they joined the small orange and the red/purple together and add in the large orange. They most likely joined them with a small nut and bolt and rapped it in electrical tape.
The voltmeter should be wired into one of the purple wires (ignition). Make sure that the voltmeter only registers when the key is on.

The voltage regulator is reading the primary ignition voltage and keeps cranking up the alternator trying to charge the battery. It's really amazing how much voltage you can get out of a 12V alternator.
I would refrain from running the engine until you get the wiring sorted out.
 

yimmyb

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Feb 22, 2017
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Where is the small orange wire and red/purple wire coming from? Alternator?
 

wrench 3

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The red/purple wire is the battery supply for everything. It comes from the battery cable on the starter solenoid and originally went to the ammeter. The small orange wire is the battery supply to the ignition switch. It originally came from the ammeter and is going to the ignition switch. Since it is now running, the two of them must be OK. You just have to add in the large orange wire from the alternator.
 

yimmyb

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Feb 22, 2017
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This is what I have as far as I can tell. From the alternator I have a large orange wire that runs to the dash and is not hooked up. A purple that splits into 3, one to ignition switch, and the 3rd to the starter slave solenoid. ( appears to be 2 into 1 on the slave solenoid). Red/ Blue splits into 3. 1 to 50 amp pushbutton reset, 1 to ignition switch and 1 to starter slave solenoid. There is no small orange wire anywhere that I can find. Do these connections sound right?, and where does the large orange in the dash connect to? Thanx for your help and patience
 

wrench 3

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Assuming that the red/blue is a faded red/purple, if the one on the ignition switch is the same size as the loose orange then that is where the orange needs to go.
It sounds like they discarded the small orange and moved the red/purple from the ammeter directly to the ignition switch.
 
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