Entry & progression
Yacht sea service is countable service. The NMC says so in terms. But the engine room has a test the deck does not — and the most common rejection in this area is a claim for engineer service on a vessel with no engine room.
"Sea service is a measure of a mariner's lifetime experience on boats, whether recreational, commercial, or military. It may be counted from the day a mariner turns age 16."
Recreational is in the list. Yacht time counts, and it counts from your sixteenth birthday. The words yacht, recreational and pleasure appear nowhere in the whole of 46 CFR Part 10 — yacht service is not excluded, it simply is not named. It is credited on exactly the same axes as anybody else's: route, tonnage, propulsion power, the capacity you served in, and the hours you worked.
The walk-in engine room test
This is the one that catches yacht engineers, and it is worth reading twice. 46 CFR 11.504: on vessels of under 100 GRT, engine service is creditable where the vessel has "a 'walk in' engine room with an engineering plant comparable to vessels over 100 gross tons."
A machinery space you crouch into through a deck hatch to change an impeller is not a walk-in engine room. A space with a plant, a workbench, headroom and a watch position is. The Coast Guard is not being snobbish here — it is asking whether the time you spent aboard actually taught you the job.
WARNING — The NMC's most common rejection in this area The NMC lists, among its most frequent reasons for rejecting an application: "Claiming engineer service on a vessel without an engine room." If the boat has no engine room, the engineer time is not there to claim. Do not spend two years building a sea service letter that the NMC will throw out on sight.
Who may sign for your time
46 CFR 10.232(a)(4) governs attestation. Owners may attest to their own service. Everybody else needs a letter from the owner of the vessel or from a credentialed officer. The NMC puts it plainly: "If you do not own the vessel, you cannot attest to your own service — even if you are serving as master."
On a yacht that means the letter comes from the owner, the management company acting for the owner, or the credentialed officer you served under. A letter you wrote and signed yourself is worth nothing, however true it is.
What the letter must actually say
Not "good crew, worked hard." The NMC is not assessing you, it is assessing the service, and it needs the facts it credits time against.
- Vessel name, official number, and the tonnage — and say which tonnage it is.
- Propulsion power of the main machinery, in HP or kW. This is the whole game in engineering.
- The route actually run — oceans, near-coastal, inland.
- The capacity you served in, and the exact dates on and off.
- The days actually worked, not the days you were on the crew list.
TIP — Build the letter as you go, not at the end Ask for the discharge letter when you leave the boat, while the captain still remembers you and the yacht still has the same manager. Chasing a signature three owners later is how good sea time evaporates.