You are the Chief Engineer onboard a general cargo vessel in excess of 1600 gross tons. To remain in compliance with the 33 CFR Oil Record Book requirements for non-tank vessel machinery space operations, which of the following operations requires an entry to be made in the Oil Record Book?

Correct Answer: Option D — Discharge overboard of bilge water which has accumulated in machinery spaces.

33 CFR 151.25 mandates that machinery space bilge water discharges be recorded in the Oil Record Book. This ensures compliance with MARPOL Annex I requirements for non-tank vessels, providing a verifiable log of all overboard discharges of oily mixtures originating from the engine room to prevent illegal pollution.