Help with identifying part on Johnson 140

[runninfarmer]

After I got my 1984 Johnson 140 running, I think I've discovered arcing, I can here a ticking sound. I've found this part sticking out of the head on the starboard side and I think this is where it's occurring. Can you please tell me what it's for? Here's a pic:




Thanks for the help!

 

[jbuote]

I'm by NO means an expert, but that looks almost like somebody added an additional temp sensor or something.. The original appears to be there. (lower cylinder, right side of head..) I don't really know.
​However, there are no wires attached to it, so if you're hearing arcing there, I'd be looking at the plug wire. It's against the head, and the boot is close to that part..
​Maybe the arcing is from the plug wire/boot to the head?

​I'm sure someone with much more experience will be along shortly though, with better answers and will probably know for sure what that part is.. LOL

​For what it's worth...

 

[GA_Boater]

That's a jury-rigged temperature sender. Looks like one out of a water cooled motor with a water jacket like a GM based motor.

If you think it's arcing, start the motor on muffs and turn the lights out. In a couple of seconds you'll know if it's arcing.

 

[GA_Boater]

I would look closely at the circled area. It appears the plug wire may be breaking down on the head bolt.

 

[rjcamel2355]

Temperature sensor is what you have there...... but, like others said that's not likely your "arcing sound" I agree check all your plug wires for breaks/knicks, that one does look like it's arcing to that head bolt. However these engines are notorious about catching a plug wire when you're putting the cowl back on, so be sure you've not doing that. Best bet is stick it on the muffs, at night, start it and watch the spark show, that'll tell you immediately if it's arcing somewhere. (Don't try to grab whatever is sparking when the engine is running.....trust me....)

 

[oldboat1]

Temp sender is not remarkable -- part of an OMC or aftermarket add-on. If you have the gauge, it's easy to hook up. A PO might have put it there as a little added insurance. Check head temps to make sure they are within specs.

For arcing issues, replace plug wires and boots. Make sure connectors are installed correctly, and that other ignition ground straps for your motor are in place.

 

[iggyw1]

It is definately a temperature sensor. It is exactly what I added to an older outboard motor that I had as I wanted to see if the temperature was rising before any alarms went off. The original sensor built in to the motor had an idiot light that went on when engine was hot and the engine would shut down if the light came on. With the temp. sensor against the head of the motor, you can see the temp. rising before the alarm sounded.

Unless you match the temp. sensor with the correct temp. gage, it will not be accurate. They come as a set and must be matched. Only one wire runs from the sensor to the gage. I know my gage was off calibration because I bought the gage somewhere and the sensor somewhere else. The gage actually read 14 degrees hotter than it actually was, (checked with infrared temp. gun) so I did not use it to see the correct temp but only as an indicator to see if the motor was getting hotter or not. Keep in mind though that as water temp heats up from one week to the next if using it on soft water in a colder climate where lakes freeze, the temperatures do change a bit anyway, but the sensor with a gage hooked up is good indicator and good insurance.