SUNDOWNER MARINE CORP HIN Decoder
Hull Identification Numbers beginning with XDO were assigned by the US Coast Guard to SUNDOWNER MARINE CORP of ANNAPOLIS, MD. The company is recorded as out of business since 1991 — common for older hulls, and useful to know when hunting parts or records. Enter the full 12-character HIN below for build date, model year, and serial — free, no account.
MIC
XDO
Location
ANNAPOLIS, MD
In business
since 1984
Status
Out of business (1991)
SUNDOWNER MARINE CORP built hulls across both HIN eras (1984–1991): boats before August 1984 carry legacy straight-year or model-year date codes; later hulls use the current month-letter format. The decoder handles all three.
Free · no account · the HIN is on the transom, upper starboard (right) corner
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SUNDOWNER MARINE CORP HIN FAQ
What does a SUNDOWNER MARINE CORP HIN look like?
It starts with the three characters "XDO" — the Manufacturer Identification Code the US Coast Guard assigned to SUNDOWNER MARINE CORP — followed by a 5-character hull serial and a 4-character date code, 12 characters total. SUNDOWNER MARINE CORP built hulls across both HIN eras (1984–1991): boats before August 1984 carry legacy straight-year or model-year date codes; later hulls use the current month-letter format. The decoder handles all three.
Is SUNDOWNER MARINE CORP still in business?
USCG records list SUNDOWNER MARINE CORP as out of business since 1991. That's common for older hulls — the HIN still decodes normally, and the out-of-business date helps date the boat and guides parts-hunting toward salvage and owner groups rather than a dealer network.
How do I decode the year on a SUNDOWNER MARINE CORP HIN?
On current-format HINs the last two characters are the model year and the 9th–10th encode the certification month and year. SUNDOWNER MARINE CORP built hulls across both HIN eras (1984–1991): boats before August 1984 carry legacy straight-year or model-year date codes; later hulls use the current month-letter format. The decoder handles all three. Enter the full 12-character HIN above and the decoder works it out, including the legacy formats.
Other builders in MD
Sources: USCG Manufacturer Identification Code database (uscgboating.org, refreshed monthly) · HIN format per 33 CFR 181 subpart C. Cite this page: CarWhere, "SUNDOWNER MARINE CORP HIN Decoder," carwhere.com/hin-decoder/xdo, last verified 2026-06-12.