1977 Merc 1150: Need Soldering Advice- About to Connect New Harness to Control Box

[kck8385]

I am installing a new external harness on my 1977 Mercury 1150. The wiring in the control box is shot also so I want to desolder the old wire connections and solder in the new.

Questions:
1. Is 60/40 rosin solder what I should use?
2. What type of flux is best?

The mechanic that was going to do this for me has taken ill and won't be available for a couple of months. I have a friend that knows how to solder but has never done a control box before.

Any advice would be appreciated.

Thank you,

Kevin

 

[merc850]

I used solder for electronic components avail. at Radio Shack and a 25 watt iron, don't overheat the switch just enough to remove/replace the wires. Tin the wires first.

 

[Chris1956]

Flux everything first. Use whatever rosin core solder you have. You may need a larger iron than 25W, as corrosion requires more heat to get the solder to flow.

You must have hot solder joints to have reliability in connection.

The original wiring harness was marine grade, pre-tinned wire. I am curious, what is the new one? Likely plain copper.....

 

[GA_Boater]

Yeah - Tinning the wire to make it solid is important. Bend the wire into a hook, slide it into the hole on the lug and squeeze it tight. You want a good mechanical fit before applying the heat and solder. Put the iron on the wire and lug at the same time and as soon as it starts to smoke, place the solder on the wire, not the iron. The solder will suck into the wire, than remove the iron and solder and let it cool. Don't move the wire while until the solder sets - Only takes seconds.

I use flux core solder, that's the rosin in the 60/40 solder.

 

[kck8385]

Merc850, Chris1956 and GA_Boater. Thank you for the replies.

Answers to your questions.
1. The new harness is copper. It is a CDI harness.
2. The existing wiring is not corroded at all. The insulation is just cracking and falling off.

My additional questions.
3. What is tinning the wire and how do you do it?
4. After you form a hook in the wire and insert it into the hole on the lug do you twist the wire around on its self or just squeeze it together?
5. The white and black lugs on the ignition each have 2 wires that attach to the lug. Do you twist them together then form a hook or just insert each separately?

Sorry if some of my questions seem simple but I want to get it right the first time.

Thanks,

Kevin

 

[GA_Boater]

Tinning is stripping off some insulation (your new harness may be pre-stripped) about 3/8" to 1/2", twisting the strands, heating the strands with the soldering iron until wisps of smoke come off the wire and touching the solder to the wire. It will melt and suck in, then remove the iron. If you have some old wire, you can practice a little to see what I mean about the smoke wisps and the solder sucking in. It doesn't take a lot of solder for tinning or soldering to the switch lugs.

The hook is squeezed over over the lug. For the ones with two wires, stick both hooks in the lug and squeeze both of them. Again, you want a good mechanical connection before soldering.

For neatness, I put some heat shrink tubing over the wire, slid away from the soldering end. After the solder joint is cool, slide the tubing down over the lug and shrink it with a lighter. Optional, but I like the cleaner look.

 

[kck8385]

GA_Boater,

Thank you. Last couple of questions before the project gets underway.

1. What size (diameter) of rosin core solder do you recommend?
2. What temp do you recommend for soldering the harness to the lugs.

Thanks again for your help.

Kevin

 

[GA_Boater]

The thinner rosin core solder, not the stuff looking like a tree trunk. is OK.

I never worry about temps with a pencil iron. I use the smoke wisps to tell me when the work is hot enough. The iron isn't heating the lugs very long, they heat up pretty fast. 60/40 solder melts a little under 400 degrees.

 

[jimmbo]

63/37 solder is a little easier to work with. I know the difference in the numbers is small but there is a difference. If you really want an exercise in frustration, try the newer lead-free solders

 

[GA_Boater]

I try not to eat the solder and never lick a joint. The lead-free stuff is junk.

 

[jimmbo]

I try not to eat the solder and never lick a joint. The lead-free stuff is junk.

Unless you wash your hands real good after handling the lead solders, and before you touch food, you will consume some


I know the lead free is junk. Just about 100% guaranteed to produce a cold joint

 

[kck8385]

GA_Boater and jimmbo,

Does the brand of solder matter? Kester vs Radio Shack?

 

[GA_Boater]

No, kck.

 

[kck8385]

Thank you,

Kevin

 

[sam am I]

I try not to eat the solder and never lick a joint. The lead-free stuff is junk.

I hold just inn teeth and only lick the gummy edge of the joint.............Nothing ever wronmg happened witdth me