Saturday, December 20, 2014

If It Fails On A Boat, It Is Probably Corrosion

Well, as I mentioned in my last post, I'm running out of things to try in fixing my deck light. Short of replacing the entire wire, the connectors up at the fixture are the only other possible failure points. So, for my first try today, I decided to replace the connectors.

Of course, I already know that the wires up at the fixture are pretty short (I had previously repaired the positive lead), so I'll need to add a length of wire along with a new connector...or I'll never be able to get a bulb connected. I don't have any "boat approved" 14 gauge wire on the boat, fortunately there is a place nearby that is supposed to have a bunch at much better than West Marine prices named Genuine Dealz.

I plug the address into my phone's GPS and head over. My phone directs me to this nondescript warehouse that almost looks like it is abandoned, except for the two cars parked near an open door. No signs or any other indications I'm in the right place, but I park and poke my head in the open door. Inside there are a lot of spools of wire and other electrical parts. Definitely a low-budget, mostly internet based operation. There were a couple nice employees that confirmed I was in the right place. I told them I was looking for some 14 gauge wire and a few connectors. They hooked up their giant spools of wire and made me a 100 foot spool while I waited. Given their prices, I ended up buying a couple spools of the marine grade tinned wire and some additional heat shrink connectors to extend my parts stock.

I return to the boat with my supplies and construct some 5 inch extension wires with spade terminals on one end and butt splice connectors on the other end. Best to assemble what I can on the ground instead of trying to do it all while swinging from the mast.

After doing what I can on the ground, I once again get out the Bosun's chair and go up the mast. Instead of using my harness, I borrowed the Bosun's chair I had used before from a friend here at the dock (I have to admit, after trying a few different chairs and harnesses, Jesse has the most comfortable one I've found). Another friend, Bill, here at my dock has an interesting rig to allow you to pull yourself up the mast. He has rigged up a couple fiddle blocks, one with a jam cleat and becket and a lot of 1/2 inch line to create a 4:1 purchase system. With this, and a rope climbing ascender, someone can pull themselves up the mast while only having to lift 1/4 of their weight. This setup made it easy and comfortable to go up to the deck light as many times as I have over the past few days.

Bill's mast rig with an eye splice I did for him.

I make my way up the mast to the light, pop the light out of the holder, and carefully unscrew the lugs on the back of the bulb enough to remove the bulb. Then the surgery begins. I cut off the existing spade connectors and strip the wires so I can attach the butt connector that is already attached to the new spade assembly. I make sure that the stripped wire is clean and in good condition. I then crimp on the new wire assemblies. This all sounds quite simple...but imagine doing it mostly one-handed while sitting on a swing hovering 20 feet over the deck of the boat. After the crimp is solid, I use a BBQ lighter (they work a bit better in the wind than the average lighter) to carefully shrink the heat-shrink end of the butt connector for a weather-tight seal. Now I have longer, weather-resistant connections for the deck light. I reattach the bulb and snap it back in the holder. The moment of truth arrives...will this Hail Mary attempt work or will I need to pull a new wire.

I make my way back down the mast, wriggle out of the Bosun's chair and head over to the electrical panel. I flip the switch....and...the light comes on!  Yes! It appears that a connector was the issue after all.

Being an engineer, I now wanted to know why this was the failure. When I was up on the mast, I did some tests, including pulling on the connectors to make sure they were well crimped, so I wanted to know exactly what the failure was. The first thing I noticed is that the crimp on connector on the ground wire is not the right size.  The wire is 14 gauge and the crimp on connector is red for 18 to 22 gauge wire...but it seemed solidly connected.  The red connector is also not sealed so weather (or on a boat, salt water, could theoretically make it's way into the connection and wire. I stripped a little bit of insulation off of the wire and found that the ground doesn't appear to be tinned wire and there was some corrosion over an inch down the wire from the connector.

Top: Bad Ground spade, Bottom: Good power spade

Checking the resistance from the spade to the cut and stripped end of the wire on the ground connector I removed, I found resistance in the 18 mega-ohm range. That's a lot of resistance. In comparison, the positive connector I removed, that I had previously replaced and only replaced again because I wanted a longer length of wire, showed 0 ohms of resistance. Clearly the ground connector is the issue.  Pulling on the wire using pliers, I was able to pull the wire out of the connector.  I found the charred and corroded remains of the wire. I guess the insulation was what was holding the connection together as well as it was.

So, it seems that corrosion slowly turned the connector into a resistor and then the heat and corrosion eventually weakened the wire to the point it would not provide enough power to light the light (I think it was more carbon and corrosion than wire).

If you have stayed with me this far in this story, here are your tips (or my lessons learned) should you run into a similar issue with electrical on your boat. First, always use heat shrink connectors anywhere corrosion may be an issue (is there any place on a boat where corrosion isn't an issue?). The combination of the shrinking and the oozing of the "glue" that seeps out as the result of the shrinking should go far to protect connections from corrosion (you can see the difference in the two types of connectors in the picture above). Next, if it looks corroded on the end, it is probably corroded where you cannot see it and it is worth replacing even if it seems to be connected. And finally, always assume it will take 10x longer to perform a task on a boat than you think it should. I'm sure there's a joke in here about how long it takes for a boater to change a light bulb...and it being 3 days by the time you fix the things found along the way.


  1. That's a great write-up, Mike. And some good information on the wiring.

    I have a does that mast rig work with an ascender? I've got a spare setup just like you have pictured from when I replaced my mainsheet and rigging. It'd be cool if I could use it to make my own mast rig.


    1. Thanks Mike, glad you enjoyed it...or at least got some tidbit of useful information out of it.

      The mast climbing rig is rigged pretty much like a main sheet might be. You just need a lot more line...over 4x the height of your mast. The ascender is used to get a better "grip" on the line you are pulling yourself up with. I would attach the ascender to the line just before it goes through the block and the jamb cleat. Then to go up (after hooking one block up to the chair and the other block to the halyard...raised to the top of the mast), slide the ascender up and then pull down on the line with one hand while controlling the line and using the jamb cleat with the other. Found it is helpful to feed the bitter end over my shoulder as I went up.

      Hope that made sense. If not, let me know and I'll try to explain better or see if I can take a picture of it rigged up.

    2. Oh, a couple more things. If you consider doing something like this, make sure the components are in good condition and can take a load well in excess of your weight...something like 5x or more I would guess...I think mountain climbers have figures what load factors you need on climbing equipment, so I'd bet that would be a good place to start. Need to take into account not just your weight...but the added forces of you bouncing around on it, etc.

      And the owner of this rig actually tied a "foot loop" to the ascender so he could use his leg instead of arm to hoist himself up.

      And I guess I need a legal disclaimer here...I used the rig, it worked...but I haven't done any sort of extensive engineering analysis of the thing so if you decide to try something like is at your own risk.