BostromMasthead Sloop1977-1984

Bostrom 31 MK II Parts

Lines here are cut for this rig

Rig: Masthead Sloop
I: 37.4 ft
J: 11.98 ft
P: 31.82 ft
E: 9.19 ft

Different version? Compare 2 related rigs

Model	I	J	P	E
Bostrom 31 MK II this page	37.4	11.98	31.82	9.19
Bostrom 31	37.4	11.98	31.82	9.19
Bostrom 37	53.02	15.09	47.24	11.48

Feet, from MAURIPRO Sailboat Data. If your mast or boom differs from every row, send us your measurements before ordering.

Line type

Grade

Compare grades

Halyards 12

Cruising

Mainsail Halyard

Diameter
10 mm (3/8 in)
Length
75 ft (22.9 m)
Hardware
Shackle

~~List Price: $240.30 USD~~
$178.00 USD

Available to order · 5 options
Performance Cruise

Mainsail Halyard

Diameter
10 mm (3/8 in)
Length
75 ft (22.9 m)
Hardware
Shackle

~~List Price: $661.90 USD~~
$491.00 USD

Available to order · 4 options
Club Racing

Mainsail Halyard

Diameter
10 mm (3/8 in)
Length
75 ft (22.9 m)
Hardware
Shackle

~~List Price: $736.07 USD~~
$546.00 USD

Available to order · 14 options
Grand Prix Racing

Mainsail Halyard

Diameter
10 mm (3/8 in)
Length
75 ft (22.9 m)
Hardware
Shackle

~~List Price: $884.29 USD~~
$656.00 USD

Available to order · 10 options
Cruising

Genoa Halyard

Diameter
10 mm (3/8 in)
Length
84 ft (25.6 m)
Hardware
Shackle

~~List Price: $361.85 USD~~
$268.00 USD

Available to order · 5 options
Performance Cruise

Genoa Halyard

Diameter
10 mm (3/8 in)
Length
84 ft (25.6 m)
Hardware
Shackle

~~List Price: $491.10 USD~~
$364.00 USD

Available to order · 4 options
Club Racing

Genoa Halyard

Diameter
10 mm (3/8 in)
Length
84 ft (25.6 m)
Hardware
Shackle

~~List Price: $928.31 USD~~
$689.00 USD

Available to order · 14 options
Grand Prix Racing

Genoa Halyard

Diameter
10 mm (3/8 in)
Length
84 ft (25.6 m)
Hardware
Shackle

~~List Price: $1,093.86 USD~~
$812.00 USD

Available to order · 10 options
Cruising

Spinnaker Halyard

Diameter
10 mm (3/8 in)
Length
87 ft (26.5 m)
Hardware
Shackle

~~List Price: $366.21 USD~~
$271.00 USD

Available to order · 5 options
Performance Cruise

Spinnaker Halyard

Diameter
10 mm (3/8 in)
Length
87 ft (26.5 m)
Hardware
Shackle

~~List Price: $503.38 USD~~
$373.00 USD

Available to order · 4 options
Club Racing

Spinnaker Halyard

Diameter
10 mm (3/8 in)
Length
87 ft (26.5 m)
Hardware
Shackle

~~List Price: $948.64 USD~~
$704.00 USD

Available to order · 14 options
Grand Prix Racing

Spinnaker Halyard

Diameter
10 mm (3/8 in)
Length
87 ft (26.5 m)
Hardware
Shackle

~~List Price: $1,119.97 USD~~
$831.00 USD

Available to order · 10 options
View moreAll Bostrom 31 MK II halyards & sheets

Made up to the lengths computed from the Bostrom 31 MK II's rig dimensions above. Colour and taper are chosen when you add to cart.

Sheets & guys 16

Cruising

Genoa Sheet

Diameter
10 mm (3/8 in)
Length
46 ft (14.0 m)
Hardware
None listed

$69.70 USD

Available to order · 5 options
Performance Cruise

Genoa Sheet

Diameter
10 mm (3/8 in)
Length
46 ft (14.0 m)
Hardware
Soft shackle

~~List Price: $242.68 USD~~
$175.00 USD

Available to order · 4 options
Club Racing

Genoa Sheet

Diameter
10 mm (3/8 in)
Length
46 ft (14.0 m)
Hardware
Soft shackle

~~List Price: $257.20 USD~~
$185.00 USD

Available to order · 14 options
Grand Prix Racing

Genoa Sheet

Diameter
10 mm (3/8 in)
Length
46 ft (14.0 m)
Hardware
Soft shackle

~~List Price: $349.60 USD~~
$254.00 USD

Available to order · 8 options
Cruising

Spinnaker Sheet

Diameter
10 mm (3/8 in)
Length
62 ft (18.9 m)
Hardware
Shackle

~~List Price: $317.81 USD~~
$235.00 USD

Available to order · 5 options
Performance Cruise

Spinnaker Sheet

Diameter
10 mm (3/8 in)
Length
62 ft (18.9 m)
Hardware
Shackle

~~List Price: $416.81 USD~~
$309.00 USD

Available to order · 4 options
Club Racing

Spinnaker Sheet

Diameter
10 mm (3/8 in)
Length
62 ft (18.9 m)
Hardware
Shackle

~~List Price: $847.39 USD~~
$629.00 USD

Available to order · 14 options
Grand Prix Racing

Spinnaker Sheet

Diameter
10 mm (3/8 in)
Length
62 ft (18.9 m)
Hardware
Shackle

~~List Price: $970.59 USD~~
$720.00 USD

Available to order · 8 options
Cruising

Spinnaker Guy

Diameter
10 mm (3/8 in)
Length
46 ft (14.0 m)
Hardware
Shackle

~~List Price: $330.88 USD~~
$245.00 USD

Available to order · 5 options
Performance Cruise

Spinnaker Guy

Diameter
10 mm (3/8 in)
Length
46 ft (14.0 m)
Hardware
Shackle

~~List Price: $407.88 USD~~
$302.00 USD

Available to order · 4 options
Club Racing

Spinnaker Guy

Diameter
10 mm (3/8 in)
Length
46 ft (14.0 m)
Hardware
Shackle

~~List Price: $833.61 USD~~
$618.00 USD

Available to order · 14 options
Grand Prix Racing

Spinnaker Guy

Diameter
10 mm (3/8 in)
Length
46 ft (14.0 m)
Hardware
Shackle

~~List Price: $926.01 USD~~
$687.00 USD

Available to order · 8 options
Club Racing

Asymmetrical Spinnaker Sheet

Diameter
10 mm (3/8 in)
Length
62 ft (18.9 m)
Hardware
None listed

~~List Price: $314.35 USD~~
$233.00 USD

Available to order · 14 options
Grand Prix Racing

Asymmetrical Spinnaker Sheet

Diameter
10 mm (3/8 in)
Length
62 ft (18.9 m)
Hardware
None listed

~~List Price: $437.56 USD~~
$324.00 USD

Available to order · 8 options
Cruising

Gennaker Sheet

Diameter
10 mm (3/8 in)
Length
62 ft (18.9 m)
Hardware
Shackle

~~List Price: $317.81 USD~~
$235.00 USD

Available to order · 5 options
Performance Cruise

Gennaker Sheet

Diameter
10 mm (3/8 in)
Length
62 ft (18.9 m)
Hardware
Shackle

~~List Price: $777.15 USD~~
$576.00 USD

Available to order · 4 options
View moreAll Bostrom 31 MK II halyards & sheets

Made up to the lengths computed from the Bostrom 31 MK II's rig dimensions above. Colour and taper are chosen when you add to cart.

Compare grades

Grade	Rope, as described on each product	Colours	Tapered option	From
Cruising7 lines	Cruiser XTS Polyester Double Braid	Up to 5	No	$69.70
Performance Cruise7 lines	DX Performance SK38 with polyester cover	Up to 4	No	$175.00
Club Racing7 lines	S Cup (Stirotec with polyester cover)	Up to 7	Yes	$185.00
Grand Prix Racing7 lines	DX Cup Dyneema SK78 core with polyester coverTN Racing - Stirotex core / Technora Polyester cover	Up to 5	Yes	$254.00

Rope names are quoted from each product's own description; prices are the lowest option for the Bostrom 31 MK II. Not sure which grade suits your sailing? Ask us.

Winches 2

Harken

Harken Self Tailing Winch Radial Size 35
Aluminum Black / Two Speed
Sized for this boat · Primary winches (genoa/jib sheets)

~~List Price: $1,477.00 USD~~
$1,033.95 USD

Available to order
Harken

Harken Self Tailing Winch Radial Size 15
Aluminum Black / One Speed
Sized for this boat · Halyard winch

~~List Price: $905.00 USD~~
$633.95 USD

Available to order
View moreAll winches

Spinnaker poles 1

Forespar

Forespar Standard Spinnaker Pole 2 1/2 in. Dia., 11 ft. 6 in. max. length (for Boats 25-30 ft.)
UXP/UXP Ends
Sized for this boat · Spinnaker pole

~~List Price: $1,320.95 USD~~
$1,056.76 USD

Available to order
View moreAll spinnaker & whisker poles

Blocks 5

Harken Block

Carbo 75mm Single
Fiddle
Sized for this boat · Mainsheet block A (4:1 fiddle)

$120.95 USD

Available to order
Harken Block

Carbo 75mm Single
Ratchet Fiddle - 150 Cam-Matic / Becket
Sized for this boat · Mainsheet block B (4:1 fiddle)

~~List Price: $319.15 USD~~
$280.95 USD

Available to order
Schaefer Spring Loaded

Lined Slide
Stainless Steel - For: 1 1/4 in (31.0 mm) T-Track
Sized for this boat · Genoa lead block

$379.00 USD

Available to order
Harken Block

Carbo 57mm Single
Fiddle
Sized for this boat · Boom vang fiddle block (4:1)

$68.95 USD

Available to order
Harken Block

Carbo 57mm Single
Fiddle - 150 Cam-Matic / Becket
Sized for this boat · Boom vang fiddle block with cam (4:1)

$184.95 USD

Available to order
View moreAll blocks

Traveler & genoa cars 4

Harken

Harken Traveler Car 1 1/16 in (27.0 mm)
Shackle - Purchase: 3:1
Sized for this boat · Traveler car (Standard 3:1)

~~List Price: $353.00 USD~~
$310.95 USD

Available to order
Harken

Harken ESP End Controls
For Travelers: 1 1/16 in (27.0 mm) - Double Sheave and Cam Cleat (Pair)
Sized for this boat · Traveler end controls

~~List Price: $588.05 USD~~
$517.95 USD

Available to order
Harken Genoa Car

ESP Slider Pinstop
For Tracks: 1 1/16 in (27.0 mm)
Sized for this boat · Genoa lead car (pinstop slider)

~~List Price: $341.00 USD~~
$299.95 USD

Available to order
Harken Block

57mm Aluminum ESP Footblock
Sized for this boat · Genoa sheet footblock

~~List Price: $145.25 USD~~
$109.00 USD

Available to order
View moreAll travelers, tracks & genoa cars

Tracks are sold by length and are not included. Ask us for the track to suit your boat.

Mainsail covers 3

MAURIPRO

MAURIPRO Canvas Shop Mainsail Cover
High Neck for booms up to 9.8 ft (3.0 m)

~~List Price: $481.62 USD~~
$382.00 USD

Available to order · 10 options
MAURIPRO

MAURIPRO Canvas Shop Mainsail Cover
MZ for booms up to 9.8 ft (3.0 m)

~~List Price: $583.71 USD~~
$446.00 USD

Available to order · 10 options
MAURIPRO

MAURIPRO Canvas Shop Mainsail Cover
Horse Blanket for booms up to 9.8 ft (3.0 m)

~~List Price: $460.63 USD~~
$365.00 USD

Available to order · 10 options
View moreAll Bostrom 31 MK II mainsail covers

Parts marked "Sized for this boat" are chosen from the manufacturers' sizing guides (Harken, Forespar, Schaefer) using this boat's published dimensions. Check your boat's equipment before ordering.

Specifications

Builder	Bostrom
Designer	Bruno BostrÃ¶m/Grandinsson
Years built	1977-1984
Rig	Masthead Sloop
Hull	Fin with rudder on skeg
Construction	FG
Length overall	30.6 ft 9.3 m
Waterline length	26 ft 7.9 m
Beam	9.1 ft 2.8 m
Displacement	7,275 lb 3,300 kg
Ballast	352 lb 160 kg
I · foretriangle height	37.4 ft 11.4 m
J · foretriangle base	11.98 ft 3.65 m
P · mainsail luff	31.82 ft 9.7 m
E · mainsail foot	9.19 ft 2.8 m
Forestay length	12 ft 3.7 m
100% jib area	224 sq ft 20.8 m²
Mainsail area	157.9 sq ft 14.7 m²
Jib + mainsail area	381.9 sq ft 35.5 m²
Cruising spinnaker area	380.8 sq ft 35.5 m²

Sail plan drawn to scale from the rig dimensions above, in feet. Hull and keel are schematic.

Source: MAURIPRO Sailboat Data, updated 2026-07-01. Always confirm against your own boat.

More for the Bostrom 31 MK II

Other Bostrom models

Questions

What Bostrom 31 MK II parts does MAURIPRO carry?

The Bostrom 31 MK II page lists halyards and sheets made up to this boat's rig lengths, mainsail covers, sails, winches, blocks, travelers, genoa cars, boom vangs and spinnaker poles sized with manufacturer guides where the boat size allows. Prices and availability shown are live from our catalogue.

How do I know a part fits my Bostrom 31 MK II?

Halyards and sheets are made up to lengths computed from the Bostrom 31 MK II's published rig dimensions (I, J, P, E). Other parts are matched with manufacturer sizing guides and are labelled as sized for this boat. Fit can still depend on your boat's year, builder and rig, so check the product details or ask our technical team before you order.

Where can I find the Bostrom 31 MK II rig dimensions?

Our Bostrom 31 MK II Sailboat Data page lists the rig dimensions (I, J, P, E) and other published data we hold for this boat. Figures come from a sailboat database and may differ from your boat as built.