1978 35 hp Johnson, electric start.

[kbh121956]

Hello Group, my first Johnson OB. Model number is, 35E78R. The harness that goes to the dash (helm) has been cut. I want to check for spark, compression, etc. I am needing help with the key switch wiring. The wires are as follows
Red/Purple stripe.
Purple/White stripe.
Yellow/Red stripe.
Black/Yellow stripe.
And a Black wire.
Also, what ignition switch do I need? Are factory service manuals available?
Thank you.

 

[Crosbyman]

wiring wise this is probably typical although not your year

https://maxrules.com/graphics/omc/wiring/25_35_82-83_elec-remote.jpg

https://maxrules.com/graphics/omc/wiring/77-78_55HP.jpg

Also, what ignition switch do I need? see diagram


Are factory service manuals available? yes but MAX rules site has free examples that can guide you if familiar with wire circuits..

purple red is fused power from solenoid B+ post to switch B+ which then gets distributed to a choke circuit, a start circuit (solenoid) yellos are usually safety interupts on a neutral switch blacks are grounds and black yellows ignition kill wires.

A post on switches feed accessories

 

[saltchuckmatt]

Hello Group, my first Johnson OB. Model number is, 35E78R. The harness that goes to the dash (helm) has been cut. I want to check for spark, compression, etc. I am needing help with the key switch wiring. The wires are as follows
Red/Purple stripe.
Purple/White stripe.
Yellow/Red stripe.
Black/Yellow stripe.
And a Black wire.
Also, what ignition switch do I need? Are factory service manuals available?
Thank you.

Does it have the big black plug on the motor or red?

 

[saltchuckmatt]

No key is needed. Unplug the motor and jump the starter solenoid. Spark gap test of 3/8 or better while checking compression numbers.

Easy to do and gives you a wealth of info.

Post the results.

 

[kbh121956]

Does it have the big black plug on the motor or red?

The big main wiring plug is black.

 

[saltchuckmatt]

The big main wiring plug is black.

That's the older one. Either buy a vintage harness or they sell a replacement harness that converts it to the red plug. More wires, more options and not hard.

Or I make my own with aftermarket connectors.

Crosbys example doesn't work for your motor but it's what it could be.

You can look up the black plug layout, follow it yourself or if you have trouble I might have the home made version written down if you want to get a newer style control box.

Either way, you have options.