Connecting AC ground to AC neutral on the boat violates the "source of new power rule" because the source of shore power is up on the land at the shore power equipment. If you connect the two on the boat you violate the rule because there is no source of shore power on the boat. So far I can't find any code to the contrary - ABYC or otherwise.
Here is the actual standard where it is laid out:
ABYC E-11
1.5.5.2 Grounded Neutral
A grounded neutral system is required. The neutral for AC power sources shall be grounded only at the following points:
11.5.5.2.1 The shore power neutral is grounded through the shore power cable and shall not be grounded on board the boat.
11.5.5.2.2 The secondary neutral of an isolation transformer or polarization transformer shall be grounded at the secondary of an isolation or polarization transformer. (See DIAGRAM 5, DIAGRAM 6, DIAGRAM 7, DIAGRAM 8 and DIAGRAM 9, DIAGRAM 10 and DIAGRAM 11 See
EXCEPTION.)
11.5.5.2.3 The generator neutral shall be grounded at the generator. (See DIAGRAM 2 or DIAGRAM 4.)
11.5.5.2.4 The inverter output neutral shall be grounded at the inverter.
The inverter output neutral shall be disconnected from ground when the inverter is operating in the charger or the feed-through mode(s). (See ABYC A-31,
Battery Chargers and Inverters.)
EXCEPTION: Exception to E-11.5.5.2.2., E-11.5.5.2.3 and E-11.5.5.2.4: For systems using an isolation transformer or polarization transformer, both the generator or inverter neutral and the transformer secondary neutrals may be grounded at the AC main grounding bus instead of at the generator, inverter, or transformer secondaries. (See DIAGRAM 5
.)
11.5.5.3
The main AC system grounding bus shall be connected to
11.5.5.3.1 the engine negative terminal or the DC main negative bus on grounded DC systems, or
11.5.5.3.2 the boat’s DC grounding bus in installations using ungrounded DC electrical systems.
The part in red that I highlighted about inverters is VERY important. Many folks try to save a buck and use the less expensive RV inverter / chargers. These may not always isolate neutral/ground when in charge mode and connected to shore power.
ALWAYS INSTALL
MARINE UL CHARGERS, INVERTERS and INVERTER CHARGERS!!!!
