We Ship Worldwide! | FREE SHIPPING! for US Continental orders over $145. Click for details.
INSTALLATION MANUAL

Sizing, toggles, sailmaker's dimensions, foil assembly, commissioning, operation, maintenance and troubleshooting for the MKIV Jib Reefing & Furling Unit 2, with the drum parts list.

DocumentHarken MKIV Unit 2 manual, v1 08/21
FormatPDF · 36 pages · 5.8 MB
LanguageEnglish
Download PDFBuy
SizingSailmakerPartsMaintenanceTroubleshooting
Harken MKIV Unit 2 jib furler

Sizing Check

Unit Wire sizes Rod sizes
7412.10 MKIV Unit 2 5/16", 3/8" · 8 mm, 10 mm -12, -17 · 7.14 mm, 8.38 mm

Toggles (sold separately)

Part no. Type Chainplate clevis pin
7412.20 5/8 Eye / jaw reversible 5/8" · 15.9 mm View system →
7312.20 5/8 Jaw / jaw 5/8" · 15.9 mm Ask us to source it →
7312.20 3/4 Stud / jaw 3/4" · 19.1 mm View part →
7312.21 5/8 Long link plate w/ toggle 5/8" · 15.9 mm View part →
7312.21 3/4 Long link plate w/ toggle 3/4" · 19.1 mm View part →

Never drill the chainplate or toggle: use the correct toggle and clevis pin. Have a rigger check an old headstay before reusing it.

Sailmaker's Notes

  • Luff tape: #6 (6/32" / 5 mm).
  • Stop the luff tape 18–24" (450–600 mm) below the head so the head lags and rolls smoothly.
  • Extend the bottom of the luff tape below the feeder.
  • Minimum inside of standard head and tack shackles: 1 3/4" (44 mm) × 11/16" (17 mm).
  • Note tack setback and the offsets above and below the sail when cutting the luff.

Rod Rigging

Part no. Description Thread
7424 -12 Rod adapter stud w/ nosepiece -12 5/8"-18 RH View part →
7425 -17 Rod adapter stud w/ nosepiece -17 3/4"-16 RH View part →
7426 -22 Rod adapter stud w/ nosepiece -22 3/4"-16 LH View part →

Rod rigging needs a Harken rod adapter stud with a mechanical lock, not adhesive alone.

Standard Package & Spares

Part no. Description Qty
7412.31 9" (229 mm) connector 7 View part →
7412.32 13" (330 mm) bottom connector 1 View part →
HFG296 Connector bushing set 1 View part →
HFG300 Plastic connector wedge set 1 View part →
HFG348 Foil screw set 1 View part →
HFG681 Trim cap set 1 View part →
HFG672 Trim cap screw set 1 View part →
H-39559 Feeder with screw and tab 1 View part →
947 Prefeeder 1 Ask us to source it →
2117 8 mm bow shackle 3 Ask us to source it →
HFG292 Drum assembly with foil clamp 1 Ask us to source it →
H-39794 Halyard swivel 1 Ask us to source it →
HFG235 7 mm single-braid polyester furling line, 70 ft (21.3 m) 1 Ask us to source it →

Drum Assembly Parts

Part no. Description Qty
HFG689 Top cover assembly w/ screws 1 View part →
HFS1060 Top cover / bottom flange screw M5 × 0.8 × 12 2 View part →
HFG690 Bottom flange assembly w/ screws 1 View part →
H-35465C Bottom flange 1 View part →
HFG691 Guard assembly 1 View part →
HFG697 Clamp with screws 1 View part →
HFS747 Clamp screw M6 × 1 × 16 SHCS 4 View part →
7412.10BASE Hub assembly 1 View part →
H-33860A Ball plugs 5 View part →
MP-127 Torlon® ball bearing 25 Ask us to source it →
MP-123 Delrin® ball bearing 100 Ask us to source it →
HCP1707 IGUS® crosspin bushing 2 Ask us to source it →

Download the full MKIV Unit 2 parts list (PDF) →

Maintenance

Clean

  • Flush the unit with soap and fresh water whenever you wash the boat.
  • At least twice a year: remove the line and flush the bearings.
  • Scrub foil grooves with a scrap of luff tape. Lubricate luff tapes with McLube® SailKote, away from the deck.

Inspect

  • Clevis and cotter pins below and inside the drum.
  • Headstay tension, swage fitting, toggle and terminals.
  • All screws, and that the foil has not dropped into the drum.
  • Replace line: 8 mm with break strength above 1700 kg (3740 lb).

Loosen the foil clamp and lower the foil before easing the backstay, so the foil does not lock against the upper terminal.

Troubleshooting

Problem Probable cause Fix
Hard to furl Halyard wrapping: angle to mast too shallow or swivel too low Optimize halyard angle; add a halyard restrainer or a wire pendant
Hard to furl Foils riding on the turnbuckle, or binding on the swage eye Raise or lower the foils at the turnbuckle
Hard to furl Salt or dirt in the bearings Flush with fresh water and detergent
Line tangled in drum Not enough drag while unfurling Use a 7402 ratchet block as the last lead
Will not furl completely Too little or too much line on the drum Rewind the drum or move the forward lead block
Furls in jerks Headstay too slack Tighten headstay and/or backstay
UV cover rolls inside Line wound on drum in the wrong direction Unwind and rewind the line in the opposite direction

Products in this Manual