72 merc 800 switchbox wiring.........different than manual

K

KT64TM

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Jul 13, 2003
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put my carbs back on today. went to reconncect my switchbox wiring and the colors are different than listed in the MERC service manual. Book says Green brown blue and red. I have green red orange yellow. The box is "color coded" but faded to the point that I can't tell red from orange. I know I know i should have taken a picture before I removed em.

anyone able to help me out here??
 
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Chris1956

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Re: 72 merc 800 switchbox wiring.........different than manual

My '73 Merc 850 is a bit different, however, maybe I can help a bit. The distributor has black, brown and white wires. On my motor they are on the port side of the switchbox.

The boat harness has red(always +12vDC) brown(Tach signal) and white wires(=12VDC from ignition switch) The coil wire was green. These are on the starboard side of the switchbox. Modern tachs do not use the switchbox signal (brown wire).

Orange is unused, grey is choke solenoid, yellow is starter solenoid.
 
Faztbullet

Faztbullet

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Re: 72 merc 800 switchbox wiring.........different than manual

The 72 uses a horseshoe trigger and a different style switchbox(393- 3736A78) and wires different than the later 4 cylinders.
 
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Moody Blue

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Re: 72 merc 800 switchbox wiring.........different than manual

I have three of those motors, two 1971 and one 1972 and they all have the same switchbox and NONE of them have the color code you describe. Colors are as Chris1956 described.

Sure yours is a 1972 model? The diagrams and manuals I have seen don't indicate the color code you are describing.
 
K

KT64TM

Petty Officer 3rd Class
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Messages
83
Re: 72 merc 800 switchbox wiring.........different than manual

Moody Blue said:
I have three of those motors, two 1971 and one 1972 and they all have the same switchbox and NONE of them have the color code you describe. Colors are as Chris1956 described.

Sure yours is a 1972 model? The diagrams and manuals I have seen don't indicate the color code you are describing.
Click to expand...


Figured it out. Looked at a diagram for a different serial number
series. My "orange" wire was the brown one and yellow was white.

Incidentally I connected the red and brown reversed, hooked up battery then
realized my mistake. I don't think the tach works now. Waiting for the fuel pump kit then hopefully it'll not rev to 3k then die.

Thanks for your replies
 
Faztbullet

Faztbullet

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15,620
Re: 72 merc 800 switchbox wiring.........different than manual

The horseshoe trigger came on 1969-72 engines , serial number ranges 3051041-3052380 and 3144219-3192962. It came with a small coil and and trigger wires where blue ,white and black. The white wire fed directly into trigger and has no hook up to switchbox. There where 2 switchboxes the 393- 3736 and the 337-4411 as the standard trigger uses the 332-2986 box. Their are still a few in my area as I still work on them for the customers, a lot of tech's and others have never seen one of these.Below is wiring diagram.
 

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