Features July 2016 Issue

A Smart, Easy Way to Rewire

A professional installer shares his secrets for rewiring your sailboat.

Running the wires for new electronics requires your best cursing vocabulary, lots of sweat, twisting body contortions, luck, and the occasional bandage. For tips on how to make this job easier, we turned to PS contributor Bill Bishop. A professional marine-electronics installer, Bishop has many ingenious ways to thread a wire from point A to point B.

PS contributor Bill Bishop drops a wire “fish” through the cabintop on a powerboat (above). Tools of the trade (above): (bottom right) wire stripper, mason’s line, electrical tape, ratchet crimper, hemostat, diagonal wire cutters, and 1 x 19 wire.

The Fish Method

The most important tool in the wire-pulling arsenal is what electricians call “fish tape” or simply a “fish.” An electrician’s fish tape sometimes works for short runs, but stiffer, 1/8-inch 1 x 19 stainless-steel lifeline wire is much better for most boat projects. A 15-foot length is usually enough.

The next thing you need is good-quality electrical tape to cover the ends of your wire fish; Bishop prefers the 3M brand electrical tape. Start about 1.5 inches away from the end of the fish and tightly spiral-wrap the electrical tape toward the end until you’re about a half-inch past the wire end. Fold the excess tape down over the wire end and spiral the tape in the other direction. Now, bend each end of your newly wrapped wire about 10 degrees. Your fish is now ready for action.

You don’t usually use the fish tape to pull a wire through. You use it to install the pull string. Bishop’s favorite string for wire pulling is 10-pound mason’s line, available at any hardware store. To help thread your fish or new cables through tight squeezes, you’ll need a lubricant. Bishop uses liquid dishwashing soap or lithium grease. To complete his wire-pulling toolkit, Bishop has a long-jawed hemostat (available at pharmacies or through medical supply stores), wire cutters, and a smartphone camera.

Pulling cables

Pulling cables

Consider enlisting a helper for the next few steps. Uncoil the cables or wires you need to pull, arrange them on the deck by connector size—largest to smallest. You are going to use the pull-string to pull each cable, one at a time, in order from largest connector to smallest.

Now, the fun part. Pushing gently, send your fish backward through the wire run to the starting point, and attach the fish to the pull string. To attach the string to the fish, use three half-hitches (see photos), then tape it securely in place. Then, pull the fish and string back through the conduit to the other end. Now, you can cut off the string, leaving about a foot still attached to the fish because you will need it again. Before you forget, tie the string you just pulled through to something so that it won’t accidentally get pulled back into the conduit.

The process is repeated with the first wire cable you are going to run. This time, however, you will be using the string to pull, not the fish wire. When attaching the string to the electrical cable, use the same technique (three half-hitches). Attach the string to the cable itself, never to a connector. You’ll want to leave plenty of extra string—about six inches—after tying the hitches. To this, you will tie a second string to leave behind for pulling your next cable. When you tape up the string and connector, try to create a smooth, narrow package. Adding some lubricant (liquid dish soap) to the lead section of the cable and connector will help slip it through the conduit.

Getting Stuck

Cables will get stuck. If you pushed the fish through a web of other cables, the connector on your new cable won’t make it through. When threading the wires through small spaces, terminals, plugs, and some other connectors may get stuck. If a fat connector keeps jamming as you try to thread it, you’ll be forced to cut off the connector, send the wire through the hole or conduit, and then re-attach the connector. Inline fuses pose a similar problem, but you can cut off and reattach those without too much difficulty. Some manufacturers warn against cutting a depth-sounder transducer cable, but we haven’t found it to be a problem as long as you don’t significantly shorten (or lengthen) the cable. If you’re forced to cut off a terminal or connector, make sure you leave a long pigtail (about a foot is good) for re-attaching the connector. The wires are color-coded, so you can match and splice the wires together.

You can also cut off RJ45-style network connectors, as well as NMEA 2000 connectors. Most NMEA connector manufacturers can supply you with simple replacements. For RJ45 connectors, you’ll need a special crimping tool. If you do cut off an RJ45 connector, be sure to save it for cross-referencing the color configuration for the new connector. It’s much easier to just keep the RJ45 connector intact, so try repeated pulls before cutting one off.

Sometimes there is a bend in a conduit that you can’t see. Don’t yank. Pull the cable back out and check for chafe. You may have to replace the line. If all looks good, you can add some dishwashing liquid to the lead end. Keep backing out and trying again. If the fish made it through the hole, your new cable should make it too.

Radar cables are thick and seem immune to a bit of extra tugging, but very small gauge wires are often part of the same bundle, and they may break if the tugging becomes too energetic.

If the cable jams repeatedly, you can try using your cellphone camera to discover what the obstacle is. Since the flash is right next to the camera lens you can take pictures through surprisingly small holes. The results my surprise you.

Cable Splicing 101

When re-splicing a plug or connector back onto the cable end, the easiest approach is to remove about an 1¼ inches off each cable’s sheath. Strip each individual wire enough to use a butt connector. Then, line up the cables so the stripped wires are alongside each other and use two tie-wraps to lash them together. Twist the corresponding wires together and crimp on a connector. Although it isn’t pretty, the tie wraps stop any strain on the connectors. This is much more secure than a simple butt connector. A few wraps of electrical tape will protect most connections. In exposed areas, you can go so far as to solder the connections and cover them with heat-shrink tubing.

Securing your Wiring

Be sure to use chafe protection where cables pass through holes or take sharp bends around corners. This would include stainless-steel tubing on binnacles and other areas with sharp edges. Split-loom hose or sections of plastic hose with slits work well in these spots.

A good rule of thumb is that the radius of any bend should be at least 10 times the diameter of the wire. Wiring should be secured well enough to stop it from sagging or moving around while underway, but not too tightly harnessed. When using tie wraps, don’t cinch them too tight. This will damage the wiring over time. Also, don’t force wiring into sharp bends while routing it. This puts added strain on the wire strands to the point of breaking a circuit.

Other Tips

Remember about the little bend at each end of the fish? Sometimes while pushing the fish through a conduit, you will encounter a tight-curved bend. The end of the fish can get stuck there, especially if the interior walls are corrugated. When this happens, it’s time to create a mini Roto-rooter. By coiling the end in your hands into a loop about 8 inches in diameter and rotating it while you push, the end of the fish will work though some fairly tight corners.

Don’t make connections and wire splices in areas where you can’t access them. This will save you headaches when troubleshooting.

When using electrical tape, leave a small tab of folded-over tape at the end. This makes it easier to remove the tape afterward.

Long-jawed hemostats will let you grab a pull-string that is visible through very small holes.

When there are multiple turns, it can be impossible to get a fish through. A good alternative is using a shop vac at one end and hand feeding the pull string with a small piece of fluff tied on the end toward the vacuum. If the fit is good, it will suck the string down into the vacuum cleaner. As a last resort, if there is existing wiring in the conduit, you can cut it and use it to install a new pull string. Ideally, it is no longer being used. If it is, you can always resplice it.

Happy wiring!

Comments (9)

I am an ABYC certified electrician and have been using 1 x 19 rigging wire for decades. It is far superior to anything I have found commercially. I crimp a small copper ferrule to each end to keep it from unwinding. Then I round the ferrule on a grinder so it slides through more easily. Also, I never used liquid soap or thick lube. These items congeal, gum up the works, and attract and hold dirt and debris. I spray the 1 x 19 with T-9 while it is coiled and do the same thing with the cable I am pulling...especially transducer cables. I not only fish the cable but protect and clean the chase at the same time. I have been at this for 37 years and have never had to cut a transducer cable and can count on one hand the number of RJ45 connectors I have had to cut. BEWARE: The color sequence of an RJ45 connector is usually reverse of what it is on the other end. These can be a real challenge.

Posted by: Captain Ed | August 16, 2019 3:55 PM    Report this comment

Wire pulling lube is much superior to liquid dish soap. Its super slippery (noticeably better than soap) and it slowly dries and the big one.... its non corrosive. Ideal is probably the most popular supplier. Big Box home stores like Menards sells it. About $8.00 for a quart and worth every penny. Once you use it you will never go back to soap.

Posted by: Dave9111 | January 7, 2019 11:00 AM    Report this comment

Fishing is an art, even when using a fish tape instead of a rod. After cursing for an hour, I broke down and asked a fellow boater who is a professional electrician for help. He did the fish instantly with no hassles.

I've found that it is usually impossible to fish the entire run at one time. Break up the run into the shortest possible lengths that allow access at both ends. Sometimes the fish will hang up in one direction but work in the other.

First I feed the fish and then pull both the wire and a tracer (pull) string attached to the fish. The end of the wire/fish must be streamlined. I use a small piece of paper towel with electrical tape to form a taper. If there is a hard edge at the end, it will very often hang up. Leave the tracer for the next time.

I bought an inexpensive endoscope (Amazon) that uses a phone app. Sending the camera cable along the route can help discover blockages. It has its own light, but being cheap the picture quality is poor but good enough.

If there are a number of other wires in the conduit or path, it is very possible to push the fish into an existing bundle, which makes it impossible to pull the wire.

Too much force just makes the bind permanent, preventing backing out.

I have also used a fiberglass rod made by Greenlee which sometimes works better than a fish tape. The rod is a lot stiffer than the tape. Search for "greenlee fiberglass fish rod". The 1x19 wire might be just as good and likely costs less. On the other hand, the rod has a hook at the end which makes it easier to attach the wire.

Posted by: Boston Barry | January 5, 2019 2:53 PM    Report this comment

Well engineered boats use plastic tubes for distributing wiring leaving plenty of space and installing spare cords for future installations. Plastic tubes prevent chaffing. And are standard practice in commercial and Navy craft. And they always use electric wires with jackets. Sadly the big volume pleasure boat builders build to a "convenience standard". After all few if any buyers ever pay serious attention to the electric installations hidden away. Surveyors oft make a bee line to see how the electric installations were done on the theory that if what's out of sight weren't done to a superior standard then most every thing else was also done to a "convenience standard".

Connecting wires with cramped butt splices and then taping over is asking for trouble. Why not do it the right way and rewire without using splices. And using wire/cables with jackets rather than the single conduct "stuff" so widely used. Butt splices usually fail. Just a matter of time. That's why commercial and Navy standards require mechanical connections inside waterproof distribution boxes. So if water sprays around the equipment still works.

We've been on many boats 40 to 50 years old that were wired up correctly with proper sized wire and cables. Where the system is still serviceable. And we've been on all too many late model production sailboats from well known builders where the wiring installations are well below acceptable standard. Long time sailors know that electric problems are typically the most common problem area. So why not do it right when making repairs and alterations. Make believe you're working on a commercial boat where lives are at stake. So the only standard is "doing it right".

Peter I Berman
Norwalk, CT author of "Outfitting the Offshore Cruising Sailboat" Paracay Pub.

Posted by: Piberman | January 5, 2019 2:12 PM    Report this comment

One more tip I learned while running wiring thru conduit for a pool job. If you have more than three 90 degree turns in the wire path, you will have to do the pull in multiple stages. It is almost impossible to pull any wire thru three bends, and four is absolutely impossible. That is why they have those "pull boxes" in metal conduit.

Posted by: rxc | January 5, 2019 11:01 AM    Report this comment

When I was needing to fish some wire over a single piece fiberglass headliner In my boat I discovered I could go around dead ends, corners and different levels by using a small piece of steel or a steel washer tied to the end of a light string and pulling it along on the inside of the liner with a very strong magnet held to the outside of the liner. Then pull a fish cable in after finding a route that worked.

Posted by: Seriously Slow | January 5, 2019 10:24 AM    Report this comment

One of the best wiring tips I know is to use a ferrous nut tied to a small line and use a small strong magnet to move the nut thru stainless steel tubing, especially with several bends or elbows.

Posted by: sdennisf@aol.com | January 5, 2019 10:07 AM    Report this comment

Easy to fallow will remember how to fish

Posted by: Wind Soar | July 3, 2016 7:37 AM    Report this comment

Easy to fallow will remember how to fish

Posted by: Wind Soar | July 3, 2016 7:37 AM    Report this comment

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