Bostrom 31 Mk II Buyer's Guide
The Bostrom 31 Mk II — also found in records as the Boström 31 Mk II or B 31 Mk II — is a late-seventies masthead sloop designed by Bruno Boström and Jens Grandinsson and built by the Danish yard Star-Boat/Plastbåde ApS, with a few thousand hulls produced. Shopping the used market means holding the documented inventory and the one known completion caveat in view rather than chasing market statistics that are not on file.
Layouts on the Used Market
The boat is equipped with six berths, a galley, and a toilet facility, and carries 100 liters of fresh water. Headroom is above average for the type. Because the design was also sold to be home-completed, interior fit and finish can differ hull to hull even when the berth and galley count is identical, so a buyer should confirm the actual joinery rather than assume a yard-standard interior.
Equipment and Common Upgrades
The masthead rig takes 30.0 m2 of mainsail plus jib, with recommended halyards of 25.6 m at 10 mm for mainsail, jib/genoa, and spinnaker, jib and genoa sheets of 9.3 m at 12 mm, mainsheet of 23.3 m at 12 mm, spinnaker sheets of 20.5 m at 12 mm, and Cunningham, kickingstrap, and clew-outhaul at 5.6 m or less on 10 mm. The fin keel is iron, and the deck is a fibreglass sandwich over a solid fibreglass hull. No upgrade prevalence is documented, so equipment should be judged against the specified lengths and diameters rather than assumed common or rare.
What to Inspect
The one documented systemic point is that the boat has also been sold to be home-completed, meaning finished quality may vary from hull to hull. A used-market inspection should establish whether a given example left the Danish yard complete or was finished privately, since that single fact drives the variance in construction standard more than any recorded defect does.
Availability and Buyer's Takeaway
No regional availability data is on file for this model. For the buyer, the takeaway is straightforward: confirm completion provenance, check the iron fin keel and sandwich deck against yard spec, and verify rigging to the listed halyard and sheet dimensions before assuming a standard example.
- Confirm whether the hull was yard-built or home-completed
- Verify six berths, galley, head, and 100 L water capacity present
- Check halyard/sheet lengths and diameters against masthead-rig spec
- Inspect iron fin keel and fibreglass sandwich deck condition
Comparable models
Similar length, displacement, and era. Open a row to compare that model's market page.
Similar boats to compare
2 similar designs| Model | LOA | Median ask | Listings · 12 mo | Active · 90 d |
|---|---|---|---|---|
| Moody 31 Mk II | 30.75' | $ 33,592 | 40 | 5 |
| Rustler 31 | 31.42' | $ 17,503 | 15 | 3 |