Your old VHF dies, you order the replacement from the same brand, and the plugs don’t match. That’s exactly what I ran into on this job. I was pulling a discontinued Garmin VHF 300 AIS and replacing it with a Garmin VHF 210 AIS, and Garmin changed the connectors between the two. The whole system had to come out.
This was a two-day job on a boat with triple Mercury 350 Verados. We started with the 20-hour service. Then we installed the new VHF at both the lower helm and the upper station, and finished with a Mercury VesselView 703 in a spot that had almost no room. Along the way I’ll show you my trick for enlarging an existing hole saw hole without wrecking the surface.
Why It Matters
Your VHF is your primary safety radio, and AIS lets you see and be seen by commercial traffic. When one part fails on a discontinued system, you’re often stuck either hunting for that part online or replacing everything. Knowing how the install goes, from cutting the dash to running cable to the upper station, helps you decide whether to tackle it yourself.
The same goes for the 20-hour service on new engines. Skip it and you leave break-in debris sitting in your oil and gear lube.
Products
- Mercury Verado 350 (x3): the engines that got their 20-hour break-in service.
- Garmin VHF 210 AIS: the new fixed-mount VHF with AIS that replaced the old unit.
- Garmin VHF 300 AIS (discontinued): the old system coming out. Its plugs don’t fit the 210.
- Garmin corded handheld mic: the remote mic for the upper station.
- Mercury VesselView 703: a multifunction engine display for the triple Verados.
- Mercury VesselView Link: connects the NMEA 2000 backbone to the VesselView. It replaces Mercury’s older NMEA 2000 gateway.
- Black StarBoard: used to make a filler plate that covers old screw holes and matches the radio.
- Snap-On reciprocating saw: for cutting the radio opening.
- Hole saws, a scrap 2×4, and blue painter’s tape: for the hole-enlarging trick.
Step-by-Step Guide
1. Knock Out the 20-Hour Service
Every new engine goes through a break-in period. The gears, bearings, piston rings, and other internal parts are freshly machined, so they wear against each other and settle in. That process dirties the oil and gear lube fast. Manufacturers require a 20-hour service to get it out, and it’s simply an engine oil change and a gear lube change.
2. Pull the Old VHF System
I got behind the active speaker and followed the cables, cutting zip ties as I went. This is where you set up pull strings so you can bring the new wires back through later.
Next, I popped the bezels off the top with a knife, took out the speaker screws, and pulled the speaker. That showed me what kind of hole I had to work with.
3. Build a Filler Plate and Cut the New Opening
The new radio wouldn’t cover the old screw holes. I cut a clean piece of black StarBoard so it would match the radio, rounded the edges, and screwed it in place. Then I put the template on and cut the opening with my Snap-On reciprocating saw. That saw is awesome for this.
I set the VHF in, screwed it down, and swapped out the mic hanger.
4. Run the Wiring
I cut out the rest of the zip ties and got the antenna wire over to the rigging tube. I tied the NMEA 2000 cable to it and pulled it up to the radio. Then I connected four things: the antenna, the NMEA 2000 cable, 12-volt power, and the cable for the upper station.
Getting that last cable upstairs wasn’t bad. A zippered canvas cover wrapped the rigging tube, and the tube was full of holes. I worked a snake through, then pulled the cable up into the second station’s electronics box.
5. Mount the Upper Station Mic
The old mic went straight up and down. The new one is corded, so it couldn’t mount that way. I put it on an angle and placed the cable hookup where the old wire used to pass through. That created a new problem: the existing hole was too small.
6. Enlarge an Existing Hole with a Hole Saw
A hole saw needs something to center on, and an existing hole gives it nothing. Here’s how I fix that:
- Use a bigger hole saw to cut a disc out of a scrap 2×4.
- If the disc is loose in the existing hole, wrap it a couple of times with blue painter’s tape until it fits snug.
- Press the disc into the hole.
- Slowly and carefully start the correct-size hole saw, with its pilot bit going into the wood.
- Once the saw is deep enough into the surface, apply pressure and finish the cut.
It works like a dream and doesn’t destroy whatever you’re drilling.
7. Make Room for the VesselView 703
The spot for the VesselView was very tight. I took some measurements and pulled the autopilot to see if I could gain space. Then I cut out some of the side where the autopilot sat and moved it over as far as it would go.
8. Tape, Template, Cut
I ran blue painter’s tape all around the fiberglass cutting area and set the template exactly where the screen would sit. I drilled a hole in one corner to get the blade in, then cut carefully around the template.
This is the beauty of a template. If it’s the right one, the part usually drops in perfectly, and this one did. I drilled the screw holes, pulled the tape, cleaned up, screwed the screen in, and slid the bezels into place.
9. Wire the VesselView Link and Set Up the Display
This hooks up differently than older Mercury setups. Mercury got rid of the old NMEA 2000 gateway and replaced it with the VesselView Link. The Link connects to the NMEA 2000 backbone and to the VesselView.
I screwed the Link box to the back of the helm, ran wires to the backbone and the back of the display, and zip-tied everything neatly. At setup, the VesselView auto-configures after you pick a language. The only thing I had to set manually was the fuel gauge.
Pro Tips
Tape every fiberglass cut. Painter’s tape keeps the gelcoat from chipping. It also protects the surrounding glass if something goes wrong, like a blade breaking mid-cut.
Use StarBoard to hide old holes. When a new unit won’t cover the old screw holes, a black StarBoard plate looks clean and matches the electronics. It beats trying to patch and fair the fiberglass.
Leave strings when you pull old wires. As you cut zip ties and pull the old harness, tie on a pull string. It turns running the new cable into a quick job.
Final Verdict
The 20-hour service is a straightforward DIY job for anyone comfortable changing oil and gear lube. The electronics swap is doable for a confident DIYer, but it’s more involved. You’re cutting into your dash, running NMEA 2000 through tight spaces, and possibly relocating other equipment like I did with the autopilot.
If you own a jigsaw or reciprocating saw, trust your templates, and don’t mind snaking cable, you can handle it. If cutting fiberglass on your helm makes you nervous, this is a reasonable job to hand off.
My biggest takeaway is the Garmin connector change. If you’re replacing a discontinued VHF, assume you’re replacing the whole system, not just the head unit.
FAQ
Is the Garmin VHF 210 AIS compatible with the VHF 300 AIS wiring?
No. Garmin changed the plugs, so the two systems aren’t compatible. You’ll need to replace the full system unless you can find the specific failed part for the old unit.
What is included in a 20-hour break-in service on a new outboard?
It’s an engine oil change and a gear lube change. It removes the oil and lube dirtied by internal parts wearing in during the first hours of running.
How do you enlarge a hole that was already cut with a hole saw?
Cut a disc from a 2×4 with a larger hole saw and tape it until it fits snug in the existing hole. Then start the bigger hole saw with its pilot bit centered in the wood.
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