Sea time is the constraint that governs how fast you progress, and it is the one candidates most often get wrong. Not because the rules are obscure, but because "time aboard" and "qualifying sea service" are two different things and people discover the difference at the assessment counter.

What generally has to be true for service to count

• The vessel qualifies. Propulsion power thresholds apply — for MEO Class 4, main propulsion machinery of 750 kW or more is the commonly stated figure. Service on a vessel below the threshold does not count toward that requirement.
• The duties qualify. Watchkeeping duty in the engine department is not the same as being aboard. Time as a supernumerary, or in a non-watchkeeping capacity, is treated differently.
• The ship is sea-going. Harbour craft and certain restricted-service vessels are treated separately.
• It is documented. Discharge certificates, the continuous discharge certificate, sea service testimonials signed by the master or chief engineer, and the training record book where applicable.

The documentation is where it fails

Engineers rarely lose sea time because they did not do the work. They lose it because a testimonial was never signed before they left, a discharge entry is inconsistent with the record book, or the vessel's propulsion power is not stated anywhere in the file.

Three habits prevent almost all of it:

1. Get the testimonial signed before you sign off, not afterwards by correspondence.
2. Check the entry against your own record the day you receive it. Dates and rank are the fields that go wrong.
3. Keep a personal running total, by vessel, with propulsion power recorded. Reconstructing this three years later from memory is how people discover they are short.

Things that commonly do not count as expected

• Time on a vessel below the propulsion power threshold for the certificate you are pursuing
• Standby, lay-up or yard periods where the vessel was not sea-going, depending on the circumstances
• Leave and non-watchkeeping periods within a contract
• Service in a rank or capacity other than the one the requirement specifies

None of these are traps exactly — they follow from the requirement being about relevant experience rather than elapsed time. But they surprise people who have been counting months on a calendar.

Watchkeeping service and the training record book

For a cadet, the training record book is the evidence that the service was structured and supervised. It is signed progressively, and attempting to complete it retrospectively at the end of a contract is both obvious and a common reason for rejection.

The watchkeeping guide covers what the duty actually consists of — which is also what the record book is asking you to evidence.

Planning around it

Work backwards. Decide the sitting you are aiming for, establish the service required, count what you genuinely hold with documentation in hand, and identify the gap. Do this at the start of a contract rather than at the end, because a contract on the wrong vessel type is recoverable if you know early.