Shore Power Options

The AC electrical system on Stella Blue is single phase 240/120 volt 50 amp system. This system has 240 volts between the red and black wires and 120 volts between either red or blank and the white common. This is the type of power used in residential services in the USA. The stove, air conditioners, hot water heater, summer kitchen grill, all run on 240 volts. Many marinas are updating to this standard to accomodate boats with these requirements.

Some other marinas have 120/208 service which is used in industrial applications, which presents special problems for the mainship 400 electrical system. JJ Kelly has provided this link which explains the problem:

JJ has also provided a great article on how to rewire the Charles transformer found on the later models of the 400 to cope with this. Click here for the article.

Not all marinas have 240/120 volt 50 amp service available, so we carry a reverse Y adapter.

This reverse Y adapter has one 230/115 volt 50 amp recepticle and two 115 volt 30 amp plugs. It contains some "smart" switching gear in the housing between the 30 and 50 amp leads. By pluging the (2) 30 amp plugs into two oppositely phased outlets on the dock (must be off the same transformer,) you will get 230 volts on the 50 amp side for your boat.

Marico has a boaters guide to AC electrical systems available online, which explains it well. It is a large .pdf file

The Marinco Version of the adapter is the "167RYN Reverse"Y" Adapter"

The Hubbel version is the "Hubbell YQ-230 Smart Y Adapter"

I have seen these things sell for over $600.00 at marinas, but internet sites have them for under $300.00.

See for good pricing on the Hubble version.

Both do the same thing. 

Below is a partial description of the adapter and how it works.


Congratulations on buying your new MARINCO 167RYN! We expect it will become an integral part of your shore power needs. The following information will insure safe operation and years of trouble-free service.

MARINCO, an American manufacturer based in Napa, California, has one of the strongest service records in the marine industry.


Read the following instructions before using the REVERSE Y.

The MARINCO REVERSE Y (cat. #167RYN) is for use with boats with 50A 125V/250 volt inlets where only 30A 125 volt receptacles are available on the dock. Boats with 50A 125 volt inlets cannot use the Reverse Y.

The two 30A 125 volt dockside receptacles must be supplied from a single power source which provides from 208 volts to 250 volts between them, otherwise the REVERSE Y will not operate.


To prevent electrocution or fire, comply with the following:

DO NOT plug the REVERSE Y into receptacles from two different power boxes. The REVERSE Y must receive power from a single source (transformer). Receptacles in different power boxes may receive their power from two different transformers.

DO NOT allow the REVERSE Y to be immersed in water. If the unit is dropped in the water, contact the factory.

STORE the REVERSE Y indoors while not in use.

ALWAYS USE the sealing collar provided with the REVERSE Y to connect the boat’s 50A shore power cord to the

REVERSE Y. The sealing collar provides a weather resistant seal between the plug and the connector. If the boat’s shore power cord is not made by MARINCO, other provisions must be made to make the connection weather resistant.