Unit 4 MKIV Racing Furler - 65-80 ft Boats, 1/2", 9/16", 5/8" Headstay, w/ 1" Jaw/Jaw Heavy Duty Toggle

Harken's MKIV furlers are designed with features for racing and performance cruising sailors. They are strong, lightweight and aerodynamic, with the performance and qualities Harken is known for – longevity, ease of use, and simplicity of installation.

These free-rolling systems make all the difference in headsail control, allowing racers and club racing cruisers to quickly furl or reef while maintaining great sail shape and optimal speed.
Smoothly and quickly unfurl your headsail instead of having to hoist a large, cumbersome genoa in light air.
The MKIV furler allows you to react quickly to changes in wind or weather. Especially advantageous if short-handed.

The drum installs over your existing forestay and turnbuckle and is adaptable to a variety of rigging options.
The lower toggle assembly accepts standard turnbuckles using swage fittings, rod terminals, or Norseman or Sta-Lok terminals.

Independent upper and lower swivels allow the sail belly to start furling before the head and tack for improved (flatter) partially furled sail shape without reducing sail area when required (and without the need for a foam-padded luff).

When used for racing, the sail feeder is quickly removeable with just a single screw and the halyard swivel can then be lowered below the feeder. Reinstalling the feeder allows for racing as a simple, non-furling, twin-groove headstay foil, with fast, easy sail changes.
The split drum removes easily for racing – allowing for the longest possible luff.

The MKIV comes in "standard" headstay lengths, but longer headstay lengths (up to a "maximum" length) can be attained with the addition of an extra extrusion and connector kit which can be purchased separately (please call for advice; 800-426-6930).

MKIV Racing features –
• Rotates around rod or wire headstay so the furler bearings don't carry the structural headstay load
• Multiple rows of durable Torlon® ball bearings help minimize friction for smooth furling under load
• Lightweight aluminum halyard swivel reduces weight aloft and features four rows of tough Torlon® bearings to withstand higher jib halyard tensions
• Aerodynamic foil shape reduces drag
• Twin groove sail feeder and double foil grooves allow for fast sail changes
• All MKIV racing foil extrusions are black
• Aluminum drum line guards, torque tube, and swivels are deep-saturation hardcoat-anodized and UV-stabilized for durability
• Drum line guards are polyurethane-coated for wear protection
• Extrusion connectors feature two sets of double fasteners and dual bushings for extra strength and support
• Split drum is easily removed for use with racing sails, providing the longest possible luff length
• Large inner drum spool diameter increases mechanical advantage for powerful reefing and furling
• Easy assembly; this unit is designed for owner installation
• Rod rigging requires purchase of a Harken rod adapter stud which must be cut and coldheaded ("mushroomed") by an authorized rod service center; see Related Products
• Designed for use with rod or 1 x 19 stainless steel rigging stays, only
• 7/16" furling line is NOT included with Unit 4 furlers, and must be purchased separately
• Seven-year limited warranty

Unit 4 MKIV racing furlers are designed for headstay lengths up to 75' 1". For headstays up to 89' 1" an extra foil section and connector kit can be purchased. Please call us at 206-632-4462 for advice.


How does the furling line work?
All headsail reefing furlers are equipped with a single furling line that leads from the furling drum to the cockpit. The sail is unfurled by pulling on the appropriate sheet, causing the line to wind into the furling drum as the sail extends.
To furl the sail back onto the headstay, simply pull on the furling line to reverse the process.


NOTE — Fisheries sells Unit 4 MKIV Racing Fulers with pre-selected toggle options, as well as one version without the required toggle, so you can select your own.
You can use the drop down menu at the top of the page to make your selection.
Choose the toggle size that matches the clevis pin diameter at the lower end of your boat's headstay or inner jibstay.
See Related Products for the Unit 4 Toggles entry.

Unit 4 MKIV furlers will also require a user-supplied 7/16" (12mm) low stretch, polyester double-braid furling line – equal to length of boat + length of foot of largest genoa + 6 ft; or measure after the furler is installed.