Max-Prop feathering propellers – Propeller
Photo: lisa bat, CC BY 2.0, via Flickr (cropped)

Max-Prop · Propeller

Max-Prop feathering propellers

The Max-Prop is an automatic feathering propeller in bronze, developed by Max Bianchi in Milan in the 1970s and still made there by Max Prop srl; PYI Inc. near Seattle sells and services it in the Americas and Asia. Its blades are geared to a central cone gear: shaft torque swings them to the set pitch ahead and astern, and they turn edge-on to the water when the shaft stops. The current range is the Easy (2–4 blades), the 5-blade Whisper, the spring-assisted Boomerang, the Easy SailDrive/Antishock and the Max Bianchi, whose pitch changes with rpm; the Classic (built until 2019), V.P., Fast and Ecowind are still found on many cruising boats. There are no seals to replace: the hub is packed with grease once a year, and the anode depends on the hub size.

Manuals & documents

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

Wear parts & part numbers

PartOEM numberAlso fitsNote
Propeller anode63ZIN · 63ZINA · 63ZIN2B2,3,4,5,6,7,8Sea Shield MP-63MM1PYI numbers: zinc, aluminium, and the pointed zinc for the 2-blade Classic (63ZIN2B, screw M4 × 25). For 63 mm Classic hubs; PYI also lists 63ZIN for the 78, 85 and 90 mm Easy hubs and the Easy SailDrive. Two 3-hole patterns, 1.70″ or 1.82″ apart; screws M4 × 20 or M5 × 20, not included. Max Prop gives the Easy 78 a hole spacing of 40.7 mm (1.60″), so measure the bolt spacing before you order. Packs of 3 with screws: 63ZINCBOX, 63ZINABOX, 63ZIN2BBOX. Sea Shield: one dealer, for shafts 3/4–1 1/8″.
Propeller anode70ZIN · 70ZINA · 99ZINRING2,3,4,5,6,9,10Sea Shield MP-70MM1PYI numbers, zinc and aluminium. For 70 mm Classic hubs (shafts 1 1/8–1 3/8″ / 30–35 mm) and 99 mm Easy hubs (1 1/4–1 1/2″); the 99 mm Easy takes it via the adapter ring 99ZINRING, which comes with the prop and is held by 3 bolts. Hole spacing 1.97″; screws M4 × 20 or M5 × 20. Packs of 3: 70ZINCBOX, 70ZINABOX. Sea Shield: one dealer, for shafts 1 1/4–1 3/8″.
Propeller anode83ZIN · 83ZINA2,3,4,5,6Sea Shield MP-83MM1PYI numbers, zinc and aluminium. For 83 mm Classic hubs and 110 mm Easy/Whisper hubs (35–45 mm, shafts up to 1 3/4″). Hole spacing 2.5″ or 2.74″; screws M5 × 30 or M6 × 25. Packs of 3: 83ZINCBOX, 83ZINABOX. Sea Shield: one dealer, for shafts 1 1/2–1 3/4″.
Propeller anode10ZIN2—PYI number for 100 mm hubs (shafts 1 3/4–2″ / 45–50 mm): 3 bolts, 2.875″ apart.
Propeller anode90SDZIN · 70SDZIN2,11,12—PYI zincs for Max-Props on a saildrive: 90SDZIN for the 90 mm SailDrive prop, 70SDZIN for the 70 mm one.
Propeller anodeZ78R3 · Z85R3 · Z90R313,8,14—Max Prop’s original zincs, M5 screws included, by the number stamped on the hub: Easy 78 (shafts up to 25 mm), hole spacing K 40.7 mm; Easy 85 (25–30 mm), K 43.3 mm; Easy 90 (30–35 mm), K 46.8 mm, 68 mm across, 4-hole version Z90R4. All three also on saildrives.
Propeller anodeZ99R3 · Z101R3 · Z110R3 · Z111R313,8,14—Max Prop’s zincs, M5 screws included: Easy/Whisper 99 (35–40 mm), K 50.2 mm, 4-hole Z99R4; Easy/Whisper/Boomerang 101 (35–40 mm), K 52.0 mm; Easy/Whisper 110 and 115 (40–45 mm), K 56.3 mm, 4-hole Z110R4; Easy/Whisper/Boomerang 111 (40–45 mm), K 57.0 mm.
Propeller anodeZ120R3 · Z126R3 · Z129R313,8,14—Max Prop’s zincs, screws included: hub 120 (Easy/Whisper/Boomerang, 45–50 mm), K 61.9 mm, M5; hubs 126 and 127 (45–55 mm), K 67.1 mm, M6, also sold as Z127R3, 4-hole Z126R4; hubs 129 and 130 (Easy/Whisper/Boomerang, 50–55 mm), K 69.7 mm, M6.
Propeller anodeZ63R3 · Z63T3 · Z63R2 · Z70R3 · Z70R213,8,14replaces Z70T3—Max Prop’s zincs for the Classic, M5 screws included. Hub 63 (shafts up to 25 mm): rounded end cap Z63R3, K 43.3 mm; triangular end cap Z63T3, K 46.8 mm; pointed 2-blade anode Z63R2. Hub 70 (30–35 mm, rounded or triangular cap): Z70R3, K 50.2 mm, which replaces Z70T3; 2-blade Z70R2. All also on saildrives.
Propeller anodeZ83R3 · Z83T3 · Z100R3 · Z100T313,8,14—Max Prop’s zincs for the Classic, screws included. Hub 83 (35–45 mm): rounded end cap Z83R3, K 56.3 mm, M5; triangular end cap Z83T3, K 60.6 mm, M6. Hub 100 (45–55 mm): rounded Z100R3, K 67.1 mm, M6; triangular Z100T3, K 72.7 mm.
Ring anodeZSD · ZSDA13,14—Max Prop zinc half-rings for the hub of a saildrive prop, 25 mm high, screws included; ZSDA (20 mm) for the Easy Antishock saildrive.
Propeller greaseLU130 · GRASSO · GRASINGR15,16,10,17,18,19—The makers disagree: PYI sells Lubriplate 130AA (LU130; calcium-based, NLGI 1) for all models, Max Prop its own very fluid lithium grease, type 0 (GRASSO, 250 g can; GRASINGR with a grease nipple).
Maintenance packMPGRKIT20—PYI grease kit for all models: grease gun, 10 oz tube of Lubriplate 130AA, nipple riser, 2 plugs, #3 Allen key.
Grease nipple & plugZERCFITKIT · INGR · GRINGR21,22,23,24,25—Grease nipples and plugs, M6, for the GREASE ports: PYI kit with 2 nipples (zercs) and 2 plugs; Max Prop’s nipple INGR and grub screw GRINGR, which closes each port and is easily lost. Take the nipple out again after greasing.
Service kit90COMBOX · 99COMBOX · 110COMBOX26—PYI Easy combo box: 3 anodes, 6 screws, grease gun, 2 tubes of grease, 2 nipples, 2 plugs, Allen keys. 90COMBOX for hubs 78, 85 and 90 mm, 99COMBOX for 99 mm, 110COMBOX for 110 mm; with aluminium anodes add A (90COMBOXA, 99COMBOXA, 110COMBOXA).
Service kit632BCOMBOX · 633BCOMBOX · 702BCOMBOX · 703BCOMBOX · 832BCOMBOX · 833BCOMBOX27—PYI Classic combo box, not for the Easy: 3 zincs, anode screws in both sizes, grease gun, 2 tubes of grease, 2 nipples, 2 plugs, cotter pins, Allen keys. The code is hub (63, 70, 83 mm) plus blades (2B, 3B); with aluminium anodes 633BCOMBOXA, 703BCOMBOXA, 833BCOMBOXA.
Propeller hardware kit633BSCRKT · 702BSCRKT · 703BSCRKT · 832BSCRKT · 833BSCRKT28—PYI screw kits for screw-assembled Classic-type props: body and end-cap screws, cotter pins, 3 anode screws, 2 plugs, nipple riser, Allen keys. The code is hub (63, 70, 83 mm) plus blades (2B, 3B).
Propeller hardware kitSVCL3P063T29—Max Prop screw set for the Classic, here 3-blade, hub 63, triangular end cap. The other sets follow the code SVCL + 2P/3P + hub 063/070/100/125/160 + T (triangular) or R (rounded end cap), e.g. SVCL2P063R, SVCL3P070T.
Fastening kit63ZINSCRKIT1 · 63ZINSCRKIT2 · 83ZINSCRKIT1 · 83ZINSCRKIT230,3—PYI anode bolt kits, 12 bolts each: 63ZINSCRKIT1 (M5 × 20) for 3-, 4- and 5-blade props with 63, 70, 78, 85 or 90 mm hub (not 2-blade), 63ZINSCRKIT2 (M4 × 20) for 63 and 70 mm; 83ZINSCRKIT1 (M6 × 25) or 83ZINSCRKIT2 (M5 × 25) for 83 and 100 mm; 110 mm takes 83ZINSCRKIT2, 129 mm 83ZINSCRKIT1.
Cotter pinsCOPINKIT · COPP-131,22,32—Cotter pins for the Classic and V.P., through the heads of the spinner and end-cap screws, cut to 1/4″: PYI pack of 25 stainless 1/16″ pins (COPINKIT), Max Prop set of 15 (COPP-1).
Propeller nutDADE063M1615 · DADE070M2015 · DADE070M242 · DADE083M24233,34—Max Prop nuts with locking pins for the 2- and 3-blade Classic: E63 M16x1.5, E70 M20x1.5 or M24x2, E83 M24x2. Unthreaded blanks: DADE063P, DADE070P, DADE083P, DADE100P.
Nut locking screws & pinsVBDEASY · GBDAEASY · SPBD063 · SPBD08335,36,37—Nut locking parts from Max Prop: VBDEASY, the 2 screws that lock the shaft nut on Easy, Whisper and Boomerang; GBDAEASY, grub screws with stem for the Easy Antishock saildrive; SPBD063 and SPBD083, 2 locking pins for the Classic nut (hub 63/70 and 83).
Propeller pullerEST078 · EST085 · EST090 · EST099 · EST101 · EST111 · EST120 · EST129 · EST130 · EST144 · EST150 · EST16138,39—Max Prop puller ring for Easy, Boomerang and Easy Antishock, one per hub number: it bolts to the anode-holder ring, and the shaft nut then pushes the prop off the taper.
Propeller shaft keyK8A · K10A · K12A · K14A · K16A40,41,42,43,25—Propeller shaft keys sold by Max Prop: K8A 8 × 7 × 80, K10A 10 × 8 × 80, K12A 12 × 8 × 90, K14A 14 × 9 × 100, K16A 16 × 10 × 100 mm. Lowered keys K08–K16 and lowered T-keys KT8, KT10 are for the shaft sizes Max Prop’s price list marks with a lower keyway. Pick by your keyway: the hub must go as far up the taper with the key as without it.
Saildrive propeller adapterASELVA44—Adapter to fit a Max Prop saildrive propeller to a Selva saildrive.

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

Service intervals

TaskInterval
GreaseOnce a year, in or out of the water; PYI calls every two years the absolute minimum, and the older 3-blade Classic and V.P. manuals ask for at least that16,10,22,45
AnodeAt every haul-out and at least once a year, even if it still looks usable; on a new berth check after a few weeks – an anode can last anything from 2 weeks to 2 years16,10
PropellerCheck the pitch against maximum rpm after fitting, and whenever the engine no longer reaches its rated maximum rpm (or over-revs) in flat water with a clean hull16
Full serviceFactory overhaul when needed: play in the blades, vibration, bent or corrosion-thinned blades46

From PYI’s Max-Prop FAQ and instruction manuals and Max Prop’s own manuals. The makers differ on the grease: PYI recommends Lubriplate 130AA (calcium, NLGI 1), Max Prop its own very fluid lithium grease, type 0. Current documents say grease yearly; the older Classic and V.P. manuals say at least every two years.

Specifications

TypeAutomatic feathering propeller; the blades are geared to a central cone gear, swing over within about 3/4 of a shaft turn and keep the same leading edge ahead and astern47
ModelsEasy (2–4 blades) · Whisper (the 5-blade Easy) · Boomerang (a spring returns the blades to feather; 5 blades at PYI, 3, 4 or 5 in Max Prop’s 2026 price list) · Easy SailDrive / Antishock (2–4 blades, with damper) · Max Bianchi (3 blades, pitch changes automatically with rpm)48,49,43
VersionsOlder models: Classic 2-blade (1978) and 3-blade (1982), 3-blade V.P. (1989), 4-blade Fast (2002), 3-blade Classic Gen II (2008)47
Years builtFirst patent 1975 (PYI dates the original to 1972); Classic built until 2019, parts and service still available; Easy family in production50,51
Propeller sizesEasy: 2–4 blades, 12–25″, shafts 3/4–1 3/4″ (PYI); Max Prop builds it for any tapered shaft of 20–65 mm / 3/4–2 1/2″ · Whisper/Boomerang: 5 blades, 20–44″, shafts up to 3″ · Classic: 2-blade for shafts 3/4–2 1/2″, 3-blade 3/4–3″52,53,49,54
SaildriveSailDrive version: 2–4 blades, 14–25″, up to 135 hp, for Volvo, Yanmar, Twin Disc, ZF, Bukh and Sillette legs (PYI); Max Prop: for any saildrive; the Classic was also made for saildrives55,53,54
Hub sizesHub (mm) → shaft, PYI: 63: 3/4–1 1/8″ · 70: 1 1/8–1 3/8″ · 78: 3/4–1″ · 85: 3/4–1 1/8″ · 90: 3/4–1 1/4″ · 99: 1 1/4–1 1/2″ · 83 and 110: 35–45 mm · 100: 1 3/4–2″ · 125: 2–2 1/2″ · 160: 3–3 1/2″2
Hub sizesEasy hub → shaft, Max Prop 2026: 78: 22/25 mm, 3/4 or 1″ · 85: 30 mm, 1 1/8″ · 90: 30/35 mm, 1 1/8 or 1 1/4″ · 101: 35/40 mm, 1 1/2″ · 111: 40/45 mm, 1 1/2 or 1 3/4″ · 120: 45/50 mm, 1 3/4″ · 130: 50/55 mm, 2″ (differs from PYI’s table: go by the number on the hub)43
Max. engine powerEasy (PYI): 78: 40 hp · 85: 57 hp · 90 and SailDrive: 80 hp · 99: 110 hp · 110: 180 hp; Classic: 63: 60 hp · 70: 90 hp · 2-blade SailDrive: 80 hp12,54
MaterialSpecial high-strength bronze50
MountingShaft tapers 1:10 (ISO), 1:12 (English) and 1:16 (SAE); other tapers on request56
Pitch adjustmentEasy/Whisper/SailDrive: set from outside, in or out of the water. PYI version: pitch bolts in bores R and L, 5 forward (16, 18, 20, 22, 26°) and 3 reverse bolts (14, 20, 24°) supplied; 1 turn = 2° ≈ 13 % rpm, 1/4 turn = 0.5°. Current Max Prop version: one grooved screw per direction, forward and reverse independent; one groove (45°) = 0.5° ≈ 2.5 % rpm10,57
Pitch adjustmentOlder models: Classic – set inside by re-indexing the central cone gear and spinner by the letter chart when assembling, 2° steps ≈ 13–15 % rpm; Fast / V.P. Fast / Gen II – 1° steps ≈ 6–7 % rpm, on the Fast pull the regulation ring forward and turn it; V.P. – pull back the adjustment ring, turn it to the angle for your rotation and push it back, in or out of the water22,58,45
Direction of rotationEasy/Whisper: switch between right- and left-hand by re-indexing the anode-holder ring behind a circlip10
LubricationGrease: PYI recommends Lubriplate 130AA (calcium-based, NLGI 1), Lewmar winch grease as a dearer alternative; Max Prop supplies its own very fluid lithium grease, type 016,17
Lubrication2–4 grease ports marked GREASE, closed with grub screws; grease nipple (zerc) and plug thread M621
Tightening torquesShaft nut, Easy family: start at 20–30 Nm (shafts under 35 mm) or 30–40 Nm (over 35 mm), then tighten on until the locking holes line up; secure with the 2 locking screws25

Good to know

  • Grease one GREASE port at a time: swap the grub screw for the nipple, pump until grease comes out at the joints between body, hub and blades, then refit the grub screw – never leave the nipple in. On a Classic, swing the blades between ahead and astern while pumping. Classics from before 1990 may have no grease ports; PYI sells a retrofit kit for them.22,59
  • Change the prop anode every year even if it still looks usable, and sand the bronze and the anode’s contact face bright first – poor contact is the usual reason an anode does nothing. To order, read the hub number (e.g. E90 → Max Prop Z90R3) and measure the bolt spacing on the old anode: PYI and Max Prop assign anodes to hubs differently. PYI’s single anodes come without screws, Max Prop’s with.16,13,3,8
  • Set the pitch by rpm: in flat water with a clean bottom the engine should just reach its rated maximum rpm. If it can’t, take blade angle off; if it over-revs, add some. Mark the pitch bolt’s position before turning it and change one step at a time.16
  • The makers describe feathering differently. PYI: motor ahead at 2–3 knots and stop the engine in forward gear; with a mechanical gearbox you can then select reverse with the engine off to stop the shaft – stopped in reverse, the blades stay open and the shaft turns. Max Prop’s current manual: stop the shaft for about a minute at 5–6 knots, then sail with the gearbox in neutral. Electronically shifted gearboxes often drop to neutral and may not feather the prop; that is what the Boomerang is for.16,10,25
  • Always idle down before shifting between ahead and astern – the blades are driven by a central cone gear, and shock loads damage the teeth. On a saildrive, make sure the thrust washer sits on the spline before the prop goes on; without it the prop runs with end play and damages the leg.10,7
  • Play in the blades, vibration or bent blades call for a factory overhaul (Max Prop in Milan or PYI, about two weeks); send the complete prop including the hub, and do not open a current Easy-family prop yourself. Never swap parts between two Max-Props, e.g. on a catamaran: each is matched and balanced as a set. A lost Easy pitch bolt can be replaced, but PYI needs the serial number stamped on the anode-holder ring.46,10

Fitted in

Boats whose builder lists it as standard or optional equipment:

  • Lagoon 410 — Max-Prop 2-blade 16″ (option) (Lagoon names no standard propeller; the November 2000 option lists offer a two-blade 16-inch Max-Prop for the 3GM30F saildrive)
  • Privilège 435 — {'en': 'Max-Prop three-blade × 2', 'de': 'Max-Prop Dreiblatt × 2', 'fr': 'Max-Prop tripale × 2', 'es': 'Max-Prop de tres palas × 2'} (Performance: feathering three-blade propellers (‘swivelling’ in the model year 2000 list, ‘Max-Prop’ on the Performance pages))
  • Pacific Seacraft 37 — Max-Prop 3-blade (option) (Option in lieu of the standard propeller in the 2002 spec sheet)
  • Valiant 40 — Max-Prop (option) (Option: a two- or three-blade Max-Prop feathering propeller, which Practical Sailor says improves performance under power and under sail)

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