Extract from IRC Rule text which is copied from the 2017-2020 ERS. Items in bold are as defined in ISAF Equipment Rules of Sailing (ERS) Part II, Definitions.
17 17 BOAT WEIGHT
17.17.1 Boat Weight is measured in accordance with the following Conditions for Weight and Flotation Measurement:
The boat shall:
be in compliance with the class rules (ie. IRC Rules)
Unless otherwise specified in the rules, any of the following shall be included:
rig including spinnaker pole(s), whisker poles and/or jockey pole
main sheet and mizzen sheet,
inboard engine or outboard engine in stowed position,
fitted berth cushions on board in their normal positions,
all permanent fixtures and fittings and items of accommodation.
Unless otherwise specified in the rules, any of the following shall be excluded:
fuel, water, variable ballast or the content of any other tanks,
portable safety equipment
and all other unfitted or loose equipment.