Advanced Marine Electrics and Electronics Troubleshooting A Manual for Boatowners and Marine Technicians

Finally, we need to check the dock’s potential.
For this, we’ll move to the shore-power pedestal:

1 With the reference electrode still in the
water, plug the DVOM’s positive lead into
the ground lug on the dock receptacle.

2 Caution: A shock hazard exists. Be sure
you have positively identified the ground
lug at the pedestal, not the hot lead.On
30 amp service, this is typically the notched
or L-shaped lug. On 50 amp service, it is a
shell connection, as shown in the photo.
See the illustrations for other common
shore-power terminal configurations.

3 Most docks will read between –400 mV
and –800 mV. A reading outside that

a basic corrosion survey 113

shell

positive lead

The shell is the ground connection on a typical 50 amp shore-power

receptacle.

100A, 120/240VPin and sleeve

3 pole, 4 wire

50A, 120/240VLocking

3 pole, 4 wire

30A, 120/208V 3ØYLocking

4 pole, 5 wire

100A, 120/208V 3ØYPin and sleeve

4 pole, 5 wire

240 and 208 Volts

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

W

G W G

W

G

YX

X

Z

Y

G

Y

X

X

Z

Y W

G

W

X Y

G

W

Y GX

W

Z

Y

X

G

W

Z

Y

X

15A, 120V

Straight blade2 pole, 3 wire

20A, 120V

Straight blade2 pole, 3 wire

20A, 120V

2 pole, 3 wireLocking

30A, 120V

Locking

2 pole, 3 wire

50A, 120V

Locking

2 pole, 3 wire

120 Volts

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

Receptacle

Plug

GG

GG

WW

WW

G

W

G

W

G

W

G

W

G W

WG

Dock and shore-cord terminal configurations, from ABYC Standard E-11. (Reprinted with permission from

Boatowner’s Illustrated Electrical Handbook,second edition, by Charlie Wing)