Bostrom 31 Mk II Buyer's Guide
The Bostrom 31 Mk II is a late-seventies Scandinavian design from Bruno Boström and Jens Grandinsson, built in Denmark by Star-Boat/Plastbåde ApS until 1984 with a few thousand hulls produced. On the used market she presents as a 30-foot masthead sloop with a fin keel and a light-racer character, but the same kit-built option that swelled the fleet also means no two examples should be assumed identical.
What to Inspect
The defining buyer risk is that some hulls left the Danish yard as bare kits for owner completion, so at a viewing you must confirm whether the boat you are considering was professionally finished or built in a backyard. Look hard at deck-to-hull joint consistency, keel-bolt bedding, and interior joinery quality; a backyard completion may show uneven laminate, poor core encapsulation in the sandwich deck, or non-standard plumbing around the 100-liter water tank and toilet. Treat any hull without a yard build tag as suspect until a surveyor confirms the standard. The iron fin keel is made of iron rather than lead, so inspect for rust staining at the hull joint and sound the keel with a hammer for delamination or section loss. Confirm the masthead rig matches the 322-square-foot working sail plan with a 135% genoa the SA/D is 19.1 and that halyards and sheets are to the 25.6-meter and 9-to-23-meter specs, as rigging substitutions hint at neglected upkeep. Beyond the kit question, spend time on the deck sandwich: probe around winches, stanchions, and hatch edges for softness that signals water in the core. Check the iron keel bolt nuts in the bilge for weeping or rust trails, and confirm the rudder bearing on the skeg-hung configuration is free of play. A compression test on the mast step and a look at chainplate tabs through the hull laminate round out a sensible pre-purchase inspection.
Buyer's Takeaway
- Verify whether the hull is factory- or home-completed before negotiating
- Sound the iron fin keel for corrosion and check bolt bedding
- Inspect sandwich deck core for soft spots near fittings
- Confirm rigging lengths and diameters against the spec
- Survey the six-berth interior joinery for amateur workmanship
- Probe deck core and rudder bearing for play or softness
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' | $ 33,214 | 42 | 4 |
| Rustler 31 | 31.42' | $ 17,644 | 14 | 0 |