Splicing different gauge wires

Just want to double check to make sure it’s ok to splice different gauge wires together for a low voltage (12 volt system) the wires won’t be drastically different (14-16, 18-20) as long as the smallest wire is still capable of carrying the load correct?

Like my other post a lot of the different accessories come with different size wires and I don’t want to buy 4-5 different gauges but two that’ll suffice for all accessories.

It will be fine


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TheLastCall said:

It will be fine


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Yep, what he said.

Yes it will be fine. Try to push the smaller wire into the strands of the larger wire inside the connector before you crimp it to make sure you have a good connection. Sometimes small wires will pull out of connectors made for larger wires very easily meaning it was not a good connection.

Optionally, they do sell "Step Down" butt splices. They aren't particularly common, however.

For example, this one [link] accepts 14-16 on one side, and 18-22 on the other, and this one [link] accepts 10-12 on one side, and 14-16 on the other.

I ordered a few for my upcoming trailer rewire.

One thing I have done when using butt connectors is to double the smaller wire over. Gives more wire in the connector to crimp. If you can the best way would to solder and heat shrink.

Never solder wires in a boat.

https://www.marinewireandcable.com/2013/11/crimping-vs-soldering-marine-cable-and.html?m=1



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TheLastCall said:

Never solder wires in a boat.

Click to expand...

If I read that correctly, it says "sole means of mechanical connection "

If a western union joint is soldered and the resulting connection is insulated with robust heat shrink tubing I'll put solder connections up against any mechanical crimp connection any day.

Very possible but your still going to get wicking, lead is not as conductive, and your possibly creating a weak point beyond the joint.


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TheLastCall said:

Very possible but your still going to get wicking, lead is not as conductive, and your possibly creating a weak point beyond the joint.

Click to expand...

AND mine are immune from vibration, salt water intrusion, corrosion and other vaporous effects. I'll take mine as a risk let others who want to risk butt connector failures take their chances. YMMV

It’s the ABYC standard. You can do whatever you want.

It will matter if ever you have a fire onboard and the insurance company find out.


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I'll ALWAYS take the risk rather than being stranded for 2 cent crimp connectors, my boating goes back to the 70's never a lost boat, or connection in seas many never dream of, no fires, no failures, AND my current boat is an TM power only. Fire? Sure, ok, I'll take the risk.

gnappi said:

TheLastCall said:

Never solder wires in a boat.

Click to expand...

If I read that correctly, it says "sole means of mechanical connection "

If a western union joint is soldered and the resulting connection is insulated with robust heat shrink tubing I'll put solder connections up against any mechanical crimp connection any day.

Click to expand...

Me too. All of my connections are soldered. 12 years and no problems yet.

TheLastCall said:

It’s the ABYC standard. You can do whatever you want.

It will matter if ever you have a fire onboard and the insurance company find out.


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I am sure my Aluminum boat will burn to the ground :shock:

Reread what it says. "Sole means of mechanical connection."

Take two wires. Lay them side by side. Flow solder between both of them.

Take two wires. Lay them end to end. Flow solder between both of them.

That is what "sole means of mechanical connection" means.

Now take two wires. Twist them together. Solder them.

The mechanical connection is the twist. The solder is not the sole means of mechanical connection. That meets the spec, as quoted in the article.


Wicking is the desired effect of soldering. That is how it works. The resistance argument is rubbish, as your mechanical connection is already in place when the solder is applied. Support the joint physically, and you have a connection that is within the quoted spec.

Like Rich’s said in his original comment solder and heat shrink.

This is wrong, you cannot do that it needs a mechanical connection as per ABYC standard. Yes the lineman union joint is mechanical but I have a sneaking suspicion that if somebody ask if they can splice different gauge wires together, they don’t know how to do a proper lineman union joint. If it’s not done properly it’s not a proper mechanical connection.

Solder needs to be properly supported when used, if it’s not it will fail.

The easiest proper way is a crimp and heat shrink. It’s cheap, easy to use, and meets the standard.

What you do is always up to you.


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TheLastCall said:

Like Rich’s said in his original comment solder and heat shrink.

This is wrong, you cannot do that it needs a mechanical connection as per ABYC standard. Yes the lineman union joint is mechanical but I have a sneaking suspicion that if somebody ask if they can splice different gauge wires together, they don’t know how to do a proper lineman union joint. If it’s not done properly it’s not a proper mechanical connection.

Solder needs to be properly supported when used, if it’s not it will fail.

The easiest proper way is a crimp and heat shrink. It’s cheap, easy to use, and meets the standard.

What you do is always up to you.

Click to expand...

"The easiest proper way is a crimp and heat shrink. It’s cheap, easy to use, and meets the standard."

Standards be damned I've had and seen Waaay.... to many crimp connections fail, and NEVER, ever a single western union AND solder AND heat shrink fail. When a boat catches fire it will not be the fault of my method. YMMV, it's not my boat

My OP said...

"If a western union joint is soldered and the resulting connection is insulated with robust heat shrink tubing I'll put solder connections up against any mechanical crimp connection any day."

I stand by that

Right on, lots of information there thanks fellas.

To be honest it is for 16 foot aluminum duck boat, so I am taking everything into account but i'm not running a whole lot of power at the end of the day (light bar and fog lights, led's under the gunnel on the inside, and as well on the outside, and a bilge) total amp draw for all of them running at once is 22 amps.
It'll be very rare for me to be using the bilge, so total amp draw of all the lights running is about 16 amps, i'll be running them off of a 32 amp hour Sealed Lead Acid battery. I live in Canada and it'll be fairly cold when I am utilizing it as a duck boat, so my battery will most likely be brought in and put on the charger after every use so its not outside in the cold and is always fully charged.

The longest time I would have absolutely all the lights going at the same time is about half an hour to 45 minutes max. Cabin lights will be used the most @ 2 amps, and someday i'll be adding a fish finder as well which doesn't draw much.

I will have inline fuses for the main battery run, the run to my headlights, a battery disconnect, and breakers at the switch panel for everything else. Everything will be grounded to a common busbar that will be isolated from the hull.

So at the end of the day I figure I'll do mostly crimp connectors, because they are easy and my wires will but tucked away into flexible conduit, so they won't be going through much abuse. My boat is also stored inside. I'll be soldering the connections to the LED's only, and sealing them with caps filled with RTV sealant for maximum waterproofing.

I have owned many boats over 30 years and have never, ever, had a soldered connection fail. I have, however, seen many crimped connections fail. I will keep soldering and enjoy worry free electrical.


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Just my .02, I usually bundle wires together, w/ zip ties & plastic corrugated conduit. That cuts down on harmonic vibration of individual wires. My experience is that corrosion kills wire, not cracks.