Wiring on 1978 Merc 70hp Blueband

[Lasermatrix]

Hi All,

I guess this is probably the best place to post this

I have a 1978 Merc 70hp Blueband outboard, the key switch is knackered, having to start with a screwdriver at the moment and there is no kill switch.

I have purchased a new kill switch and ignition switch, which I have mounted on the dash.

The ignition switch is a 3 pole type, off, accessory, start.

On opening the merccontrol remote, I discover the keyswitch in there has more than three pins

Basically I have the following:

Red : Terminal A on keyswitch, always Live
White : Terminal F on keyswitch, live only in accessory
Orange : Terminal E on keyswitch, live only when starting
Black x 2 : Terminal D on keyswitch
Offcolour Yellow? : Terminal B, goes to common on Gear Interlock Microswitch
Yellow to NC connection on Gear Interlock Microswitch

Grey + White (also links back to accessory terminal) : to Choke Switch
This would make sense as the choke is only operational when keyswitch is in accessory position.

White wire from socket on front of remote to Terminal F - Accessory
Brown wire from socket on front of remote disappears into loom to engine
Black wire from socket on front of remote to Terminal D

The question is, what wires do I need to re-route to the keyswitch on the dash.

Clearly Red is the main feed and should go to the main terminal on the new keyswitch

The blacks must be ground

And the white wire should go to the accessory terminal on the new keyswitch

I'm guessing the Orange Wire should go to the start position on the new keyswitch

The other question is, where should I wire the kill switch?

I have searched high and low for a wiring diagram for this engine, even purchasing a manual off eBay, but unfortunately it turned out to be for newer engines which seem to have a different colour coding.

Can anyone who has delved into these engines before shed any light on this for me, before I wire it up incorrectly and blow something I shouldn't

I would like to wire in Nav lights as well, so that I presume would attach to the white and black wires.

Best Regards
Chris

[Lasermatrix]

In a follow up to this:

it would appear the Orange wire is the kill wire and is connected to ground when the key is in the off position.

Therefore that presents me with a little problem, the new keyswitch makes no connection when in the off position.

So, I think the best course of action would be to wire in a 12v relay to the accessory position and wire in the orange/black to the relay, so that when the relay is energised, the connection from the orange wire to ground is broken and when the key is turned to the off position, the power will be removed from the relay and the connection will be remade between orange and white, this would also allow me to parallel wire the kill switch across those connections.

Anyone have any further thoughts? Am I even on the right track

[Lasermatrix]

To end this story..

I finally completed the rewire of the ignition system, fitting a new keyswitch and kill cord to the engine, the orange wire was indeed the kill wire.

The relay works a treat, it energises when the key is turned to accessory, thus breaking the kill wires ground connection and then when the key is turned off, the relay de-energises and the kill connection is remade. copious amounts of hot glue and sealant now cover said relay