Hubbell YQ100 Plus Smart-Y Adapter 100A from 2x 50A Shore Power

The Hubbell YQ100 Plus Smart-Y is the shore power adapter you need when your boat is rated for 100A 125/250V service but the marina you're tied up to only has 50A receptacles. The YQ100 Plus combines two 50A receptacles into a single 100A feed, with internal logic that verifies the dock wiring is safe before allowing power transfer. It's not a cheap product, but neither is your boat, and the consequences of getting marina shore power wrong on a yacht-class boat are not the kind of thing you want to gamble on.

Two cables come out of the boat-side connector: an A-leg and a B-leg, each terminated in a fully molded 50A 125/250V Hubbell shore plug. Plug both into separate marina receptacles that are wired correctly and the unit combines them into a 100A feed to the boat. Or plug only the A-leg into a single 50A receptacle and the unit operates as a 50A adapter, giving you flexibility when you arrive at a marina that doesn't have two adjacent 50A pedestals available.

The Smart in the name is the internal logic system. The YQ100 Plus monitors three things continuously and only allows power to flow to the boat if all three check out. First, plug engagement: both plugs (or the A-leg in single-receptacle mode) must be fully seated. Loose-plug arcing on a 50A pedestal is the failure mode that starts dock fires, and the Smart-Y refuses to play. Second, polarity: the unit checks that hot, neutral, and ground are wired correctly at each receptacle. Marina wiring errors are surprisingly common, and a reverse-polarity feed will eventually kill electronics or galvanically corrode through-hulls. Third, phase: when combining two 50A receptacles, the phases on the two pedestals must match for the 100A combined output to be sane. The unit verifies phase relationship and refuses to combine out-of-phase feeds.

Indicator lights on the boat-side connector show polarity status for each input plug and overall safe-operation status for the combined output. Green means good, amber or red means stop and check the dock wiring before you do anything else.

The construction is everything you expect from Hubbell marine wiring devices. Fully molded plugs (no field-assembled parts to fail), thick wire jackets sized for 100A continuous duty, integrated cord clamps at every termination to prevent strain on the conductors, and an environmentally sealed enclosure that keeps rain, humidity, and salt fog out of the internal logic and contact points. The molded enclosure is more compact and lighter than older Smart-Y designs, which matters when you're carrying it from the boat to the dock.

One critical safety point that the Hubbell documentation calls out and we want to repeat: this adapter MUST be connected to an onboard center-tapped isolation transformer or a shore power converter. Combining two separate shore power feeds into one boat circuit creates ground loop and phase mismatch risks that an isolation transformer is specifically designed to manage. Without one, you're at real risk of stray current corrosion, equipment damage, and electric shock. If your boat doesn't have a properly installed and verified isolation transformer, do not use this adapter. Period. Talk to your yard about adding an isolation transformer before you buy this adapter.

For boats that DO have a properly installed isolation transformer, the YQ100 Plus is the right tool. Charter operations rotating between marinas with different power capabilities, sportfishers and motoryachts cruising the East Coast or Gulf with mixed marina infrastructure, and large catamarans and trawlers where 100A service is the norm onboard but not always at the dock. We sell most of these to professional captains running boats in the 50 to 80 foot range.

Install. There is no permanent install. The YQ100 Plus is a removable adapter that lives in your shore power locker. The boat-side 100A connector mates to your existing 100A boat inlet. The two 50A plugs go to the marina pedestals. Connect, verify the indicator lights, then turn on shore power at the boat panel. To disconnect, reverse the order: turn off shore power at the panel first, then unplug the marina pedestals, then unplug the boat inlet. Always.

One more practical note. The plugs and the body together weigh about 30 pounds shipped, and the cables are heavy. Carry the unit in two hands when you're moving it from the boat to the dock or vice versa. Dropping a 30-pound assembly of molded plugs onto a fiberglass dock or into the water is the kind of expensive mistake that's easier to avoid than to recover from.

Hubbell standard limited warranty applies. Same-day shipping before 3 PM ET on in-stock units. We can confirm fit against your specific boat-side inlet (most 100A boats use the standard Hubbell HBL5100C9W boat inlet, but verify before ordering) and we're happy to refer you to electricians who specialize in yacht shore power if you need install or commissioning support.