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Mercruiser Wire Harness Help

J

Jgallo17

New member
Hello, first post here
I am currently rebuilding my Ford 351W marine engine. I am at the point of wiring up the engine; however, the wire harness is making me scratch my head. Is anyone able to provide a pin layout for this harness? I have looked all over, yet I have not seen anything. The harness itself has 9 pins; however, where it connects to the engine has 10 labeled spots. Any help is appreciated. View attachment harness.jpg
 
See schematics, May not be your exact schematics but they show what you ask about

Old dash.jpg








old 351.jpg
 
Little follow up here. When turning the engine over the wire that comes from the R post on the starter becomes HOT and smokes. Attached to the positive post on the coil is the R post wire, alternator wire, choke wire, and a wire that goes to the distributor. On the negative side, there is a negative wire that goes to the distributor and a negative wire that runs back to the female plug that is Brown.

The R post wire is being backed from what i could assume is the alternator, as when the alternator is unplugged the wire does not heat up at all. However what is confusing me is that the alternator is what supplies the coil when operating in the run position. Can someone help with this? Photo is attached
 

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That is a Ford 888/302 engine yet the wire diagram in post #4 is for a GM 198/305. So you must not referance that diagram.

From your last picture with the coil & all sorts of (read that as "too many/DIY handiwork" in my opinion) wires, you need to find a correct wire diagram & start from square 1. I can tell you those terminal ends are not original 1970s material.
 
Droid said:
That is a Ford 888/302 engine yet the wire diagram in post #4 is for a GM 198/305. So you must not referance that diagram.

From your last picture with the coil & all sorts of (read that as "too many/DIY handiwork" in my opinion) wires, you need to find a correct wire diagram & start from square 1. I can tell you those terminal ends are not original 1970s material.
Click to expand...


888 schematic.jpg
 
There you go, coil negative gets brown to shift interuptor switch & to distributor (color not shown but I believe brown or black).
Coil positive gets tan to solenoid "R" terminal and whitish resistor wire.

For some reason someone has installed a ballast resistor on yours. I'm also seeing 5 wires on yours.

Like I said above, start from scratch. Use correct color wire (16 ga is ok, avoid 18 it's to likely to fail from vibration. Quality red not blue terminals & good crimper.
 
If the DIYer has removed/destroyed the whitish resistor wire from choke heat to coil positive, then use solid white with a ballast resistor.
 
Droid said:
If the DIYer has removed/destroyed the whitish resistor wire from choke heat to coil positive, then use solid white with a ballast resistor.
Click to expand...
I believe that that resistanve wire, even though it shows at choke, actually is/should be burried in the harness as a multi wire juction. (ignition on)
 
I’m just confused as to where the coil gets power when the key is in the RUN position. Does the R terminal provide power when the key is in RUN, and not start?
 
Schematic of Dash wiring and pin outs of connector.

I added Blue type for Jgallo as he may remove the Amp meter and replace with Volt meter.

Either way, Alt output is fed to amp meter and Key switch at the same time coming from Pin 4 (RED /White) and out put side of Amp meter goes all the way back to engine Pin 6 (RED) and connects to Battery + to charge battery at solenoid where Battery + is also connected.

Very stupid way of doing it back then.



888 schematic.jpg




888 dash schematic.jpg
 
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R terminal is 12volts + only when key is in start position. This 12 volts gives a hotter spark for starting only. When key is released coil power comes thru the resistor wire. Probably 9 or 10 volts.
 
Droid said:
R terminal is 12volts + only when key is in start position. This 12 volts gives a hotter spark for starting only. When key is released coil power comes thru the resistor wire. Probably 9 or 10 volts.
Click to expand...
No resistor wire, No points, Pertronix kit and blaster coil....

Prior owner butchered the wiring.......
 
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