'47 Merc starter motor question.

[66miles]

Hi all,
Yesterday while pondering starting issues, I noticed the battery cable connection to the starter motor was loose. Tried tightening it only to discover that the thread on the brass stud is so beat it's almost non-existent, so the 1/2" nut just spins around. Not a prob (I thought to myself), I'll just drop the starter motor out and re-cut a new thread onto the existing stud. Getting the starter out proved easy as pie. When I took a closer look at the battery connection it became obvious that the solder joint to the stud inside the motor has failed, causing a bad connection (the terminal becomes hot while cranking). Has anyone tried re-soldering these connections without completely dismantling the motor?

 

[Kurt in NJ]

To me completly dismantling is removing the field coils ---this doesn't need to happen

I doubt you can get enough heat to the connection to properly solder it without taking the armature out, and you need a good sized soldering iron, too small of an iron will heat things too hot and chance of damaging insulation, at least a 3-400 watt iron, I use a 600 watt iron and it heats the junction in a few seconds(about5) to soldering heat, this way the heat doesn't travel too far ---a long time ago I used 2 150 watt guns, the insulation was smoking some after the 30 seconds to a min it took to heat and everything got hot.

There used to be a replacement "stud" that fit over the stripped one( try the "HELP" brand at auto parts store), but if you have to go in you might as well replace it with a new one ---and remember that you want new nuts too, the power flow is from the stud to the threads--then to the side of the nut to the terminal ----and if a washer is used it can't be corroded too ---rusty nuts could have been the start of your problem

 

[66miles]

Thanks Kurt. Good information, especially about the 600W iron. I was wondering how to get enough heat into that solder-joint. I could see by looking at it that the 100W iron I use at work wasn't gonna cut it. Is it a big job pulling the insides out of these motors so I can get a decent shot at that solder-joint.