Scanmar · Wind-vane self-steering

Monitor windvane

The Monitor is a servo-pendulum wind-vane gear that Scanmar International in Richmond, California, has built since 1975: a small airvane turns a paddle in the water through a gear linkage, and the paddle swings sideways and pulls two lines that steer the boat’s own wheel or tiller. One size fits boats from about 20 ft to over 60 ft; Scanmar designs a four-point mount for each boat, and gears built since 1997 are 316 stainless (304 before). The Monitor TopHat is the same gear with the airvane on a separate turret on a davit or arch, and the optional E-Rudder (MRUD II, successor of the original MRUD) slides over the paddle and turns it into an emergency rudder. Many parts depend on the serial number (safety tube Types I to IV, new latch from 1994), and the routine maintenance is a fresh-water rinse: no grease anywhere.

Manuals & documents

The links go straight to Scanmar. We host no manuals or drawings — the manufacturer’s copy is the current one.

Wear parts & part numbers

PartOEM numberAlso fitsNote
Service kit8101,2—Bearing kit: every plastic bearing and bushing of the gear, including the airvane balls, pilot shaft bushings, pendulum roller bearings, actuator shaft bearings and bushings, plus the wooden loading dowel. Scanmar’s refit after about 15,000 miles or five years; keep the old parts aboard as spares.
Onboard spares kit8011,3—Cruising parts kit for long passages: the wear parts plus small, hard-to-find bits such as bearings, bushings and spring clips.
Service kit2651—Pendulum rebuild kit: roller bearings 31, two set screws 32, two flanged bearings 34, two Delrin washers 41 and the wooden dowel 117 for loading the roller bearings.
Service kit5751—Actuator shaft rebuild kit (the link from airvane to gears): two Delrin bearings 54 and two bushings 74, plus parts 55, 75 and 75.1 from the parts list. The complete actuator shaft is 570.
Service kit5151—Airvane base rebuild kit: the Delrin flanged bearing, Delrin washer and two retaining rings at the foot of the airvane.
Roller bearing311,4,2—Pendulum roller bearings (Delrin), one set per gear: at each end of the pendulum strut and in the pinion gear. Load them over the wooden dowel 117 so they do not spill. Also in kits 265 and 810.
Ball bearings (loose balls)3 · 2 · 41,2—Airvane pivot bearings: 3 is the set of loose Delrin balls (18 at each end of the airvane tube), 2 the bearing cone (two per gear), 4 the press-fit race. The ball set is also in kit 810.
Gear set36 · 371,4,5—Pinion gear 36 and ring gear 37, 13 teeth each, stainless; early Monitors had bronze gears. The correct mesh is marked with an arrow; Scanmar’s gear re-alignment sheet shows how to reset it.
Airvane1 · 1.1 · 1.2 · 8251,4,6—1 small (heavy-air, formerly called standard), 1.1 large (light-air; many owners use it most of the time), 1.2 stubby for low overhead clearance; 825 is the pair of one large and one small. Current vanes are 8 mm Lexan Thermoclear. The TopHat takes the same vanes.
Control line820 · 820.1 · 820.2 · 1121,4—6 mm (1/4 in) custom Spectra: pendulum line 820 by the foot, standard set 820.1 (2 × 18 ft, aft cockpit), long set 820.2 (2 × 30 ft, centre cockpit). 112 are the two 6 ft lines of the wheel adapter, also 1/4 in.
Turning block815 · 49 · 4201,7—Block kit 815, fits all Monitors: four in-frame roller sheave blocks 49, two external turning blocks 420 and their fasteners. The turning block bracket is 87 (two per gear).
Safety tube (breakaway link)67.1 · 67.21,8,9,10,11,4—The deliberate weak link between hinge and paddle. 67.1 (1-1/2 in diameter) fits Types II to IV: 12 to 22 in long in 2 in steps, standard 14 in, 0.049 in wall up to 16 in and 0.065 in from 18 in; the hole and slot pattern follows the serial number (Type II 1694–2175, Type III 2176–4026, Type IV from 4027, June 1995). 67.2 is Type I: 1-5/8 in, serial 0–1693 (to December 1989). Carry a spare.
Water paddle (servo blade)61 · 6011,4—61: stainless skin over a stainless shaft, foam-filled, supplied with 10 ft of 1/4 in safety and lift line (66). 601 is the paddle complete with hinge/latch assembly 440, safety line and safety tube.
Hinge set440 · 44 · 761,2,12—Hinge/latch assembly 440: hinge 44, latch 47, latch spring 48, 5 ft trip line 46 and two hinge pins 76 with retaining rings 76.2. Pulling hinge pin 76 (single-hole clevis pin; 76.1 has a hole at each end) takes the whole paddle assembly off.
Latch47 · 48 · 48.11,13,14—New style since 1994, with an arm for the release lanyard; supplied with trip line 46 and a cotter pin. It needs the double-coil spring 48; old-style latches take the single-coil spring 48.1. Scanmar’s retrofit sheet warns that the new latch may not fit older Monitors, so give the serial number.
Wheel adapter100 · 1801,15—100, complete and all stainless: mounts on either side of the wheel, with clutch and locking pin. 180 is the basic wheel adapter rebuild; drum 101 and disk 102 are also sold on their own.
Tiller bracket7011,16,2—Tiller attachment kit, cam-cleat style; Scanmar’s tiller adapter sheet (2010) shows the installation. On a tiller the lines are crossed to opposite sides.
Mounting bracket83.2 · 83.4 · 821,4—Hull brackets: upper U-bracket 83.2 and lower U-bracket 83.4, two of each, with two studs, nuts, lock and fender washers, through-bolted to the hull. End fitting 82 (two) joins each lower tube to a frame leg.
Mounting tube89.2 · 88.1 · 88.21,4—Sold by the inch, cut and bent to the boat’s mounting drawing (bending is charged per bend, part 90): upper tubes 89.2, 1.9 × 0.065 in; lower tubes 88.1, 1.25 × 0.049 in; diagonal tubing 88.2 with one end flattened and drilled.
Fastening kit861,2—Mounting bolt 5/16-18 × 1 in, drilled for safety wire, with lock washer and wire; holds the tubes to the hull brackets. Engine vibration can loosen them: check them now and then and keep them safety-wired.
Emergency rudder847 · 8451,17,3,2—E-Rudder / MRUD II, complete (847): stainless rudder sleeve that slides over the water paddle, a bracket that locks the pendulum, and upper and lower Spectra support lines. It fits modern-era paddles, so check the serial number with Scanmar. 845 is the pendulum bracket alone: on boats under about 30 ft of moderate displacement it may let the paddle itself serve as emergency rudder. Fit and test it in port before an ocean passage.
Mounting bracketSG1,3—SwingGate: hinged Monitor mount for open or reverse transoms and swim platforms.

Numbers checked against the sources below on 13 October 2026. Always confirm against your serial number and exact type before ordering.

Service intervals

TaskInterval
Fresh-water washWhenever you reach port (rain helps too): flush every bearing point with fresh water. Never use grease or spray lubricants15
Season checkOften and always before a long passage: check the pendulum lines for chafe, shift the chafe points and replace worn lines; check the mounting bolts for loosening from engine vibration and keep the leg bolts safety-wired2
Full serviceAfter about 15000 miles or 5 years of use: renew all plastic bearings and bushings with bearing kit 8102

From Scanmar’s Monitor manual (part 2, maintenance) and the Monitor FAQ. Scanmar gives no calendar; bearing wear is counted in sea miles or years of use.

Specifications

TypeServo-pendulum wind-vane gear: the airvane turns the water paddle through a gear linkage, and the swinging paddle steers the boat’s own rudder through two control lines to the wheel or tiller. Steers down to about 4 kn of apparent wind18,15
VersionsMonitor: airvane on the frame. Monitor TopHat: airvane on a separate turret on a davit, arch or rail, linked to the frame by a low-friction splined cable; same airvanes, mounts and E-Rudder6
Years builtSince 1975, still in production; 316 stainless since 1997, 304 stainless before18,15
SizesOne size for all boats, from a Flicka 20 to a Sundeer 64, with many installations over 60 ft. Scanmar says the limit is the boat’s steering (how much wheel it needs) and the transom, not its length15
WeightAbout 23 kg (52 lb) with a typical mounting system18
MaterialFrame, paddle skin and paddle shaft stainless steel (316 since 1997); 13-tooth stainless pinion and ring gear (early Monitors: bronze gears); Delrin bearings; airvanes 8 mm Lexan Thermoclear with plastic rod reinforcement (older ones 4 mm birch plywood); paddle foam-filled15,1,4
DimensionsAirvane height: standard (small, heavy-air) 940 mm (37 in), light-air 1143 mm (45 in), mizzen vane 660 mm (26 in). The control lines attach 457 mm (18 in) from the pendulum pivot for 1:1 line travel4
Line sizePendulum lines 6 mm (1/4 in) custom Spectra/Dyneema: standard set 2 × 18 ft (5.5 m) for an aft cockpit, long set 2 × 30 ft (9.1 m) for a centre cockpit1
MountingFour-point mount through-bolted to the hull: two upper tubes into sockets on the frame, two lower tubes to the frame legs, each ending in a U-bracket; diagonals on long mounts. Scanmar designs the mount and its drawing for each boat; the gear comes off with four bolts. Height: about 15 cm (6 in) of the paddle top out of the water with the boat loaded for cruising4
ControlWheel adapter (fits either side of the wheel, turns it up to about half a turn each way from centre, clutch for instant disengagement) or tiller kit. Hydraulic steering needs an emergency tiller on deck and a bypass valve15
LubricationNone: loose Delrin balls (18 at each end) in the airvane pivot, Delrin roller bearings in the pendulum strut and pinion gear, Delrin bearings in the actuator shaft, all designed to run wet. No grease and no spray lubricants2,15
Warranty3 years for the original owner3

Good to know

  • Have the serial number ready before ordering parts: the Monitor has had more than 50 design changes since 1975 and some parts no longer interchange. It is stamped on the port side of the frame’s cross-tube (the “D-ring”) between the upper tube sockets. Buying used? New gears ship with the custom mount, a wheel adapter or tiller kit, two airvanes, a spare safety tube and the Dyneema lines; check what is missing.1,3
  • No grease anywhere: the Delrin bearings are meant to run wet, and grease mixes with salt water into a paste that adds friction. A fresh-water hose-down in port is the whole routine maintenance.15
  • After a circumnavigation or about five years, play in the gear usually means worn plastic bearings and bushings; kit 810 renews them all. When rebuilding the airvane pivot, hold the 18 loose Delrin balls per end in place with something water-soluble such as shaving cream, and load the pendulum roller bearings over the wooden dowel. Keep the old parts aboard as spares.2
  • The pendulum lines do the hardest work. Check them before every passage and shift the chafe points; lead them through good low-friction ball-bearing blocks with sheaves of about 2 in and as few turns as possible. On a wheel they must enter the adapter from below, or the gear steers the wrong way. To change one at sea, stitch the new line to the old one and pull it through; if it has parted, tie the pendulum off first.2,4
  • The safety tube is a deliberate weak link that bends before the gear or the transom is damaged. Carry the spare, tighten both bolts until there is no play at all, and do not shorten a tube to lift the paddle: a shorter pendulum has less power. Mounting the gear too low is a common fault (Scanmar says it never sees one too high): it adds drag and load.4,2
  • In heavy weather never leave the paddle floating horizontally, which overloads the hinge; when heaving-to, cleat the pendulum lines so the paddle stays centred. In a marina or whenever the gear is idle, pull hinge pin 76 and take the whole paddle assembly off.2

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Sources

  1. scanmarinternational.com/monitor-parts
  2. scanmarinternational.com/_files/ugd/d14bae_3b3a352d087344619f92ad81508c18cd.pdf
  3. scanmarinternational.com/monitor-pricing
  4. scanmarinternational.com/_files/ugd/d14bae_f2ca7cc4bfb34aeab59702e6925dbed0.pdf
  5. scanmarinternational.com/_files/ugd/d14bae_4fada76d02b147cbaacfe7b5e90a60d4.pdf
  6. scanmarinternational.com/_files/ugd/d14bae_7957f3efab32449ca953c7ae9e1ad55d.pdf
  7. scanmarinternational.com/product-page/815-block-kit
  8. scanmarinternational.com/_files/ugd/d14bae_68d6761ce20f4f07a2d86e607e5f5e79.pdf
  9. scanmarinternational.com/_files/ugd/d14bae_848d29e95cd546da843ab596758a9c66.pdf
  10. scanmarinternational.com/_files/ugd/d14bae_a5f2e60329f84e2bac4258da119a3eb8.pdf
  11. scanmarinternational.com/_files/ugd/d14bae_601ed35e3ca741958ac8f5217244a46f.pdf
  12. scanmarinternational.com/_files/ugd/d14bae_4f964e98474147f79a90be04fdbff360.pdf
  13. scanmarinternational.com/_files/ugd/d14bae_0129d49096d7467a94588ff3765ac8a0.pdf
  14. scanmarinternational.com/_files/ugd/d14bae_cd15d74859ec46b3981bb427950ad6b6.pdf
  15. scanmarinternational.com/monitor-faq
  16. scanmarinternational.com/_files/ugd/d14bae_ba5827e7734b4c189024afe557c4c778.pdf
  17. scanmarinternational.com/m-rud
  18. scanmarinternational.com/monitor-windvance-hp

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