1993 Bayliner Mercruiser 4.3 Starts and Dies after letting go of ignition switch. Need Wiring Diagram

mars22

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Aug 8, 2013
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7
I just bought a 1993 Bayliner 2050, it has the mercruiser 4.3/Thunderbolt IV. The guy said he bought it, it ran once on the water and the second time he had it out it wouldn't start. He said he took it to a mechanic and the mechanic said he needed a whole new complete power unit for $6500(absolutely laughable). He sold it and now it is my problem.

It starts but dies the second you let go of the key switch. I checked the oil pressure switch and bypassing it changes nothing. I think it might be the ignition switch itself. I need pictures and diagrams for the ignition switch. It only has 3 wires coming out of it, purple, red, yellow/red stripe. I have 12Volts across the red to both the purple and yellow wires until I crank it and then they lose voltage. I suspect it is wired very wrong and most likely my problem.
 

Lou C

Supreme Mariner
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Nov 10, 2002
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13,048
There is the B terminal (red wire) the I terminal (purple wire) and S terminal (yellow/red wire). Make sure that the I terminal has battery voltage when you turn the ignition on, and then continues to when you turn to start. If not the switch may be bad.
 

Scott06

Admiral
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Apr 20, 2014
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6,765
Check man overboard switch what you describe are classic symptoms of it
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Check for power on the purple wire

Red=battery power
Purple=ignition
Yellow/Red=start
 

mars22

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Aug 8, 2013
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The man-overboard switch has been bypassed(has power, engine has no spark when it is disconnected). I really need a wiring diagram but my google-fu has been weak.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
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Messages
50,270
The man-overboard switch has been bypassed(has power, engine has no spark when it is disconnected). I really need a wiring diagram but my google-fu has been weak.
the factory wiring for the engine to the key switch is in the factory mercruiser manual.

however the wiring colors are standard and the wiring color to function is in the electrical stickies.

check voltage at your switch as indicated in post #4
 

mars22

Cadet
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Aug 8, 2013
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7
Fixed: I bypassed the ignition switch and hotwired it and it fired right up. Just a bad ignition switch. Thanks for your help!
 
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