Non-waterproof Connectors are not Reliable in Damp Areas

"Shotgunning" is Bad Because it is Ineffective

It's Easy to Make Bad Splices, Particularly with the Wrong Tools.

There are so many strange and terrible things illustrated in this image. 

This menagerie came out of an Erickson with an Atomic 4 engine.  The engine had a disturbing tendency to die at the most inopportune time.  It would work for months and then it would die and not restart while, say,  approaching the slip.  The owner had done every "tune-up" trick possible.  New plugs, new plug wires, new distributor, new coil.  The owner really liked the boat and was about to repower just to get reliability.  I was called as a last resort.  I started the engine and moved the engine wiring harness around.  The engine died.  I flexed the connector in the harness and sometimes the engine ran fine and sometimes it cut out or wouldn't start.  I cut the entire obscene connector bundle out and directly spliced every wire to its mate.  Problem fixed, happy owner, and I get paid for the minimum service call.  

This is also a lesson on how NOT to fix a problem.  The owner just replaced ignition components serially, figuring he'd eventually get to the culprit.  This mindless method is called "shotgunning" because you just blast away and hope you hit the right thing.  I do not "shotgun."  I figure out what is wrong and then fix it.  From experience, if you do not understand why something stopped working or started working again, you will be back to fix the real problem later.  Shotgunning is not a method of finding a problem.  It is the absence of any method.

No disrespect to shotgun owners intended, it's just a common figure of speech.

At this point we must stop for a background note: the electrical wiring on every engine is built as a harness at the factory.  The wiring harnesses is then fitted to the engine.  They put a connector on the end of the harness so they can test the engine and so the engine can be mated up with the control panel harness when it's installed in your boat.  After that point the connector serves no useful function, sort of like your appendix.  If someone pulls the engine for a major rebuild, they're probably going to cut and re-splice the wires anyway, just like they did here.  As you can see from the variations in wire splicing technique employed, all the harness wires have been disconnected and re-spliced on both sides of the connector at one time or another.  But no one took out that pointless, troublesome little connector.

The two halves of the engine harness connector are the black things in the middle of the photo with all the wires coming out.  The connectors cannot be unplugged from each other as their pins are pretty solidly corroded together, just not always making contact with each other or the wires.  On the detail enlargement to the right, the swelling and unevenness of the right side of the connector indicates corrosion.  The blue tint of the corrosion at the top of the connector, where the red wire passes through, indicates this is the positive wire from the battery, which is hot whenever the battery switch is on.  The bright blue stuff is mixed copper salts.  The metal in an exposed positive conductor electrolytically corrodes until the wire or connector dissolves. 

This connector is not waterproof, like most old engine connectors.  The engine compartment is just wet enough just frequently enough to damage the connector.  If the connector was in a wetter place, it would have failed sooner.

The heat-shrinkable butt splices shown here were probably made by 3M or their licensee.  These splices are just short of magic when you need a fast, waterproof connection.  But Caution, Caution.  You must use a suitable crimp tool or you will pierce the insulation.  Also, you must use a real heat gun that can be temperature controlled.  The adhesive melts not too far from the temperature that destroys the heat-shrink plastic.  You will need more heat than is commonly used for heat-shrink tubing.

Eight of the butt splices shown above have been done more or less correctly.  These include the blue, purple, gray and brown wires on the left.  If you look closely, you can see the melted adhesive that extruded from the end of the shrunk connector.  This is a good sign, but.

The installer used a butane lighter or matches to shrink these splices rather than a heat gun.  It is very hard to heat shrink splices this unevenly with a heat gun.  Matches and lighters leave black soot deposits or scorch the wires.

The blue wire on the left and tan wire on the right look as though they were not completely shrunk and the adhesive adequately melted.  Heat-shrink connectors must be heated longer than it takes to shrink down the plastic jacket.  They must be heated long enough to melt the adhesive onto the wire.  



The tan wire on the left looks like the left side of the splice was heated long enough to start charring the plastic wire insulation and possibly the splice itself.  Again, this reveals the use of matches, which cannot be used to apply controlled heat.  



The red and yellow wires have heat-shrink butt splices, but no one bothered to shrink them.  You can see a little blue deposit inside the connector on the right side red wire.  This is a copper corrosion product, a sure sign this was a positive wire and it got wet.  If you had to pick only one wire to waterproof, make it the red wire.  Waterproofing the red wire is probably all that was actually required next to an engine.



The splices covered with short lengths of electrical tape are the strangest of all.  What can this person have been thinking?   If a butt splice needs to be waterproof, it should be a heat-shrink splice properly shrunk.  Applying a few inches of electrical tape may make you feel good, but it does nothing to waterproof the connection.  On the contrary, it just hides your mistakes and holds water at the connection.


One more detail:  Negative exposed connections do not corrode when energized and wet.  If you must leave some connections un-waterproofed, let them be the negative (black) wires.

Finally, a quiz to find out if you've been paying attention.  In the picture of a little plastic six-pin connector to the right, which wire was DC positive?   



Added January 14, 2007,  re-edited July 1, 2009.