1969 Chris Craft Roamer 46 Refit: Installing 12kva Bridgeport Magnetics Marine Pucks!

Having a functioning shore power system onboard is a priority that needs to happen before our Roamer splashes.

As I described briefly in my last article on installing the main breaker, in September 2022 I made temporary shore power connections to 240 volt service and powered up the original isolation transformer. I’d re-installed that 185lbs Acme-brand beauty in 2016, but this was the first time I’d powered it up since we bought the boat for a dollar in December 2007. The transformer was incredibly noisy, and though it was putting out 240vac in total, one leg was putting out 175 and the other was only 65.

I looked around at the options and decided the best approach for my aluminum boat was to go with a stacked set of two 6kVA torroidal tranformers from Bridgeport Magnetics. They call them Marine Pucks (pdf), and they’re a HUGE improvement over the original isolation transformer.

Rather than mounting them in the original location, I found a good spot in the bilge space under the galley floor. I ordered the transformers and, based on the diagrams in the Marine Puck brochure, got busy making the mount and re-routing the 6AWG cables that will feed the shore power selector switch in the main electrical panel.

Aluminum angle floor supports will double as Marine Puck panel mounts

I already replaced most of the mahogany OEM floor supports with aluminum angle, but I had a couple of leftovers that will come in handy now.

I’m glad I kept this scrap piece of marine-grade 3/4″ plywood

It’s exactly the size Bridgeport Magnetics’ technical drawings say I need for a Marine Puck mounting panel.

Laying out where supports need to go and holes need to be drilled

The aluminum supports have to line up with the mahogany floor joists under the galley, but the hardware for them can’t interfere with the Marine Puck enclosure or mounting holes.

Putting a radius on the corners so there won’t be sharp edges

The Bridgeport Magnetics’ technical spec sheet said the Marine Pucks are 12.6″ in diameter, and this radius is seven inches from the main center support bolt hole, so removing this material in the corner shouldn’t affect how the tranformers are mounted.

After rounding the panel edge with a 1/2″ router bit, I sanded it smooth

The panel is ready to be epoxy coated

Back at the shop, I trimmed the floor supports to size

Then I welded a rectangular piece of 3/16″ plate to the end of the angle

That plate is the base that will sit on the plywood floor in the bilge.

Couple of spot welds on the inside with full beads on the outside

I applied a heavy coat of US Composites’ 235 epoxy with a bit of white tint to encapsulate the mounting panel

This is in the bilge, so I’m really not concerned too much about appearance. The important thing is that this wooden panel won’t ever be affected by humidity in the bilge.

I applied a light coat of the same epoxy to the aluminum support that will be in contact with the panel

Without the epoxy coating, humidity in the air would condense on the aluminum and cause the white powder (aluminum oxide) to form over time.

Tef-Gel goes in each bolt hole

304 stainless 1/4-20 bolts, with large washers to spread the load on the wooden panel, complete the mounting panel

It’s ready to install! Which is good, because the Marine Pucks were scheduled to arrive the next day.

The mounting panel fit perfectly!

There are some tools Harbor Freight sells that are outstanding despite being relatively cheap, compared to more famous brands. One is the 4×6 metal cutting bandsaw I used to cut the aluminum angle above. Another is their hydraulic portapower kit. I used it to jack up the mahogany floor joists 1/8″ so I could slide the mounting panel into place.

We’re ready for Marine Pucks!

Each 6kVA Marine Puck weighs 80lbs

I’m going to have to ‘get Egyptian’ to install these little monsters.

I lifted it up to the top of the first flight of steps…one step at a time

Then I slid it across the scaffolding

In the pictures above, you can see part of the 6′ long, ongoing repair where the Interlux fairing compound didn’t stick to the base aluminum. That repair is still not done because it’s just been too cold to prime or paint. Sometimes it’s warm enough, but that’s only because rainy weather is warmer than clear days this time of year. And when it’s too wet, it’s not a good idea to paint in this humid tent.

At the top of the steps, I put in a temporary bridge

After sliding the transformer aboard, I carried it to the salon door

Then, over the threshold and down the steps, through the salon, and into the galley

Then repeated the process

These are impressively constructed, but something was off

The Marine Pucks came with all of the mounting hardware and a handy schematic label had been applied.

The enclosure is PVC plastic and the torroidal transformer is potted in epoxy, not varnish and resin like a more conventional isolation transformer

The torroidal transformer also has no joints in its core. And because its enclosure is plastic and it’s potted in epoxy, there’s no reference to ground. There’s literally no way for stray current to find alternate paths back to the source. So long as the boat is wired properly, there can be no ground fault or shock risk. This is the same principle in effect when a squirrel runs along a 480 volt high tension wire and…nothing happens. Because there’s no return path for the electicity back to the source so long as the squirrel stays on the high voltage line.

Squirrels who build nests near neutral or ground lines suffer different fates…

Bridgeport Magnetics’ engineer explained that the varnish in conventional transformers breaks down over time, and the joints between the hundreds or thousands of thin steel plates in the core start moving a bit. That’s what makes them become noisier and noisier over time. They claim that simply can’t happen with Marine Pucks.

Hmm…that’s an odd wiring diagram for 240 volts

The 120v diagram looks right, but the 240 one is definitely not for US installations. We use split phase L1 and L2, with 120v on each leg to get 240v, and a 0v neutral and L1 or L2 for 120v circuits. Fortunately, there was a more detailed instruction brochure in the box that also showed the wiring for US installations.

This will take some serious ‘gettin’ Egyptian’

I need to shove the Puck up behind the panel, then rotate it to align with the panel, and push it forward and slightly uphill until the mounting holes align. Remember…it weighs 80lbs. This was not an easy task.

The Puck is rotated (with some difficulty and cussing) to match the panel

Another 1/4″ and I can install the main support bolt

1/2″ diameter center bolt and wires are installed

I went to grab the second Puck, and that’s when I realized I’d forgotten to install some additional hardware on the first one. So I pulled it out and found another small problem.

The technical drawings didn’t show these grommets…

If you look closely, you may be able to see that the hole in the grommet is the same size as the hole in the PVC enclosure. That’s not right. It should be smaller so the grommet can fit in the hole. Also, the grommet hole is 3/8″, but the bolts included in the kit are 1/4-20. That’s a bit disappointing.

With great effort (and some cussing) I forced the grommets in the holes

It looks goofy, but I’m sure it’ll work fine. The 1/2″ center bolt is the main support.

I decided to crimp and seal up the cable connections while I had both Pucks on the galley floor

One Blue Seas 4-terminal block rated at 30 amps for each Puck will suffice

I used adhesive-lined ring and butt shrink connectors for all of the Puck wire connections.

Liquid Tape seals off the orange cable, which the schematic says is “unused”

I wonder why they include it if it’s unused…

Gettin’ Egyptian ver. 2.0 went much smoother than the first time…with far less cussing

Input cable connections on Puck 1 are done

Pro tip: use a wire tie to hold the wires securely to the center support inside the Puck

I didn’t do that the first time around, and the wires kept getting between the mounting panel and the center support. I’d push the Puck away from the panel, reach in and move them out of the way, but as soon as I moved the Puck back to the panel the wires would once again get in the way. Using a wire tie solved that problem.

Pro tip #2: after rotating the Puck into alignment with the panel, I pushed the input and output wires through their respective holes in the panel. Then shoved the Puck forward a bit while tugging the wires through the holes. That also helped keep the wires from getting in the way of the center mount.

With the terminal blocks secured to the underside of the galley floor and all connections made per Bridgeport Magnetics’ schematic, I went up and turned on the main breaker.

L1 and L2 to neutral yields 122v!

L1 to L2 shows 245v!

No smoke! No drama! How refreshing!

When I first turned on the main breaker, there was audible humming from the Pucks, but it got quieter and quieter over a minute or so until they were absolutely dead silent. Just like the brochure claimed! How refreshing!

Next, I flipped the shore power selector switch to Dock, which energized the distribution breaker panel for the first time since (probably) 1985. All circuit breakers were, of course, off.

OEM Simpson volt meter shows the breaker panel is getting juice!

With the shore power system commissioned, I can finally–after 10 long years–get rid of all of the extension cords I’ve been using to bring electricity from the outlets in the yard inside. This is major progress.

Next up in our 1969 Chris Craft Roamer 46 Refit: Salon Electrical Panel