Johnson 140hp 1977 wire identification. ?????

[phillnjack2]

hi guys, I am hoping someone can help us out with a electrical wire fitting .:facepalm:
We are working on a friends 1977 Johnson 140hp model no 140ML77S.
trying to get it all back up to a good running order and things are going fine so far.
Now we have found a couple of wires that we just cannot work out where they go and what they really are for.

on the top of the engine near the back is the engine lifting bracket, on this bracket is some kind of
sensor or sender that is an original fitting by the looks of it.
the colours of the 2 wires coming from it are pink with yellow strip and pink with white stripe, the pink could
be a faded purple due to age etc, so it could be purple with white and purple with yellow.
The wires then travel under the back of the flywheel and come out by the rectifier.
Both wires have ring terminals on them but we have no idea what they should be connected to and what the sensor/sender is.

I think its some kind of heat sensor, but cannot find anything listed for these colour wires .

can anyone please tell us what this sensor is and where to put the wires please

any help will be greatly taken on this topic.


phill..

 

[Joe Reeves]

Re: Johnson 140hp 1977 wire identification. ?????

What you are speaking of is an obsolete heat sensor for a thermal fiunctioning choke solenoid. It was a failed attempt at an automatic choke system that OMC corrected as per the following bulletin data.


(Temperature Actuated Choke Solenoid Conversion)
(J. Reeves)

Various OMC engines that were manufactured in the later 1960s thru the early 1970s, for example the 1969 55hp Evinrude/Johnson incorporated a dual stage choke solenoid...... easy to identify as they have two wires leading to the solenoid, one purple/white, one purple/yellow.

The purple/yellow is attached at the engine wiring terminal strip to another purple/yellow wire that led to a heat sensor. The initial stage, with the key ON, (purple/yellow), when cold, would keep the choke pulled in half way until the engine warmed up, at which time it would release and open the choke butterfly.

The second stage (purple/white) is attached to another purple/white wire at the engine terminal strip which leads to the choke switch. When the switch was engaged, the choke closed etc.

The problem with this setup is that as the engine got older, the thermostat acted up, water pump became weak, whatever, the heat sensor failed to operate properly and the choke would not release from that half closed position. This would cause the engine to run in a rich fuel mixture condition (flooding, loading up).

The cure to this problem, via a service bulletin from OMC was to remove the solenoid purple/yellow wire from its original location and connect both of the solenoid wires (purple/yellow & purple/white) to the engine wiring harness purple/white wire at the engine terminal strip.

The above change would allow both solenoid wires to be energized when the choke switch is engaged, pulling the choke butterfly in firmly..... and only when the choke switch is engaged.

 

[phillnjack2]

Re: Johnson 140hp 1977 wire identification. ?????

thanks joe

so its best to just leave the wires off or connect both of them to the purple and white ?
the choke does seem to be working ok when we use the choke switch and the control box though.
maybe this explains a little hard to start sometimes as if we don't have enough choke ?


phill.

 

[Joe Reeves]

Re: Johnson 140hp 1977 wire identification. ?????

It's not a "or" type suggestion. Get rid of that heat sensor... cut the wires off close and toss them away. Then connect the choke solenoid wires as explained. That willl allow a full 12v to energize both windings of that dual wiring choke solenoid which will cause it to really slam in when energized.

 

[phillnjack2]

Re: Johnson 140hp 1977 wire identification. ?????

thanks joe will do that next thing on the list

once again thanks.