Anyone who has pushed a wire through a T-top tube knows how it goes. It moves fine for the first few feet, then it hits a bend and stops, and you end up yanking on a pull string while worrying you’re about to strip the jacket off a network cable. On this Technicians Tuesday I installed the tower on a brand new 2019 36-foot Yellowfin with triple 300 hp Mercury V8s. The boat came down on a trailer, and the tower had to ride separately because of all the bridges, so every harness, hose, and antenna wire had to be fed through the rigging tubes by hand.
In this post I’ll show you the method I use to run anything through tower or T-top tubing, plus how I set the tower, finished the upper station, and got the boat ready for water.
Why It Matters
Your tower tubes carry your engine data, steering, trim tab wiring, electronics network, lighting, and VHF antenna. If a wire gets nicked on the way in, or pinched when the tower comes down, you’ll get intermittent electrical faults that can take hours to trace. A careful rigging job keeps you from pulling the tower back off later.
Products
- Wire harness depinning tool: removes the pins from connector plugs so harnesses fit through tight tubes.
- Electrical tape: tightens and smooths the wire bundle so it doesn’t snag inside the tube.
- Zip ties: keep the stacked bundle from shifting while you pull.
- Clear Glide cable pulling lubricant: cuts friction so the bundle slides around bends.
- 3M 4200: marine adhesive sealant for the tower bases. I use it here because it doesn’t run the way 5200 does.
- Mercury Heavy Duty Racing prop hardware: the three-washer prop nut setup used on these V8s.
Step-by-Step Guide
Step 1: Get the Tower Console Up Top
Set the tower console up top first so you can run cables from the rigging tubes up into the console and send the radio antenna wires down to the lower station console.
Step 2: Depin the Engine Data Harnesses
Don’t try to force a harness through a tight rigging tube with the big plug still on the end. It’s much easier to depin it. I used the depinning tool to pull the pins, taped them up so they’d fit in the tube, ran the harness, and repinned it at the other end.
Step 3: Run the Starboard Side First
The starboard side had the lighter load: the engine data harnesses and the antenna wire going downstairs. I finished it first.
Step 4: Tackle the Port Side, Biggest End First
The port side is the hard one. It holds the steering hoses, trim tab wires, chart plotter network cables, the light wire, and the VHF antenna wire. Always start with the hose or wire that has the biggest end and work down from there.
Step 5: Build a Smooth Bundle
This is the best way I’ve found to run anything through a rigging tube:
- Stagger the ends of the wires so they stack on top of each other rather than bunching into one fat lump.
- Zip tie the bundle so nothing shifts.
- Include an extra wire or string in the bundle to serve as your next pull string.
- Wrap the whole thing in electrical tape so it’s tight and smooth with nothing to snag on.
- Coat the bundle with Clear Glide or another cable pulling lubricant.
- Feed it up into the tube while someone pulls from the top, working it around any bends.
For a single wire, wrap the wire and pull string together, add a couple of zip ties so they don’t unbraid, smooth it over with electrical tape, and lube it before pulling.
Step 6: Seal and Set the Tower
With the VHF antenna wire run downstairs, all the rigging was through. I put 3M 4200 on every tower base and lowered the tower slowly, pushing the rigging up as it came down so nothing got pinched. Then I installed the bolts and tightened everything down. I had to pull the speakers from the lower station to reach the inside of the bolts.
Step 7: Rig the Upper Console
Once the tower is down, rigging the upper console is mostly plug and play. The steering components are the exception and take more work.
Step 8: Prep the Engines and Install the Props
I checked the oil level, topped off the gear lube, and installed the props. The Mercury Heavy Duty Racing prop hardware has three washers: a big one, a flat one, and a concave one. The big washer goes against the prop, the flat one goes in the middle, and the concave one faces out toward the prop nut. If you see a gap between the two outer washers, the concave washer is facing in, so flip it. Then tighten the nuts.
Step 9: Bleed the Steering and Water Test
With the boat in the water, I bled the steering system, checked for leaks, and then installed the bottom of the T-top.
Pro Tips
- Depin before you pull. Forcing a large connector through a tube is how pins get bent and jackets get torn. Depinning takes a few extra minutes and saves you from chasing a fault later.
- Always leave a pull string in the bundle. When you need to add a wire next season, it’s already in place.
- Choose 4200 over 5200 for tower bases. 4200 stays where you put it, and it doesn’t lock the tower down the way 5200 would if you ever have to pull it.
Final Verdict
Running rigging through tower tubes is doable for a DIY owner who’s patient and has a helper. Getting the tower itself on and off is the hard part. You need the equipment to lift it and at least two people to lower it safely while guiding wires. Depinning connectors and plumbing the steering also demand some confidence. If you’re adding one or two wires to an existing T-top, you can do it yourself with the bundle method above. A full tower install on a new triple-engine boat is a shop job for most owners.
As for the boat: it handled beautifully. It topped out at 62 mph at 6,200 rpm with full fuel, burning about 73 gph. That works out to 62 ÷ 73 ≈ 0.85 mpg at wide open throttle, which is impressive for a 36-footer on triple 300s.
FAQ
How do you run wires through a T-top tube?
Stagger the wire ends, zip tie them into a bundle with a pull string, wrap it smooth with electrical tape, and lube it with a cable pulling lubricant like Clear Glide. Pull from the top while feeding from the bottom.
Should I use 3M 4200 or 5200 for a boat tower?
I use 4200 on tower bases. It doesn’t run like 5200, and it isn’t as permanent, which matters if the tower ever has to come off.
Which way does the concave washer go on a Mercury prop?
On Mercury Heavy Duty Racing hardware, the concave washer faces out toward the prop nut, the flat washer goes in the middle, and the big washer sits against the prop. A gap between the outer washers means the concave washer is facing the wrong way.
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