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OWNER'S MANUAL

Fitting, greasing, pitch setting (blade angle to inches of pitch by diameter), changing rotation, feathering technique, maintenance, removal and locking-nut fitting for the Max-Prop Easy feathering propeller in 3, 4 and 5 blades.

DocumentMax-Prop Easy & Whisper (3, 4, 5 Blade) Instruction Manual
FormatPDF · 12 pages · 2.2 MB
LanguageEnglish
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InstallationPitchChange RotationUseMaintenanceLocking NutProducts
Max-Prop Easy & Whisper (3, 4, 5 Blade) — Instruction Manual

Installation

The prop arrives assembled for right or left rotation and at the pitch agreed at order. Max-Prop parts are NOT interchangeable between propellers: if you receive more than one, keep their parts apart.

  • Key: fit the prop like a fixed propeller. A correct key has almost no side clearance and a very small clearance on top, so it cannot push the prop off centre.
  • Nut: tighten and lock with the two Allen head screws. Sail drive: then tighten the centre bolt and lock it with the set screw through the side.
  • Zinc: fit and secure with the three Allen bolts; zinc and prop faces must be clean for good contact.
  • Grease: fill the body through the holes marked GREASE with the supplied grease fitting until grease oozes from the joints between the central part and the hub; then repeat with the forward fitting. Use only grease approved by Max-Prop.
  • Feather check: rounded trailing edges of the blades aft, blades perfectly lined up (Fig. 2).
  • Before launching: hold the shaft and check the blades swing freely from forward to reverse with light effort, the body is full of grease, and there are zincs on prop and shaft.

Pitch Adjustment

Size diameter and pitch as for a fixed propeller, then fine-tune. Engine does not reach the desired RPM: reduce the blade angle. Engine over-revs: increase it. Each 2 degree step changes engine RPM by about 13% at the same boat speed.

Diameter 10° 12° 14° 16° 18° 20° 22° 24° 26° 28° 30°
12" 4 4.8 5.6 6.4 7.2 8.2 9.2 10 11 12 13
13" 4.3 5.2 6 6.9 7.8 8.9 10 10.9 12 13 14
14" 4.6 5.6 6.6 7.6 8.6 9.6 10.7 11.8 12.8 13.9 15.1
15" 4.9 6 7.1 8.1 9.2 10.3 11.4 12.5 13.8 15 16.2
16" 5.2 6.4 7.6 8.6 9.8 11 12.2 13.4 14.7 16 17.3
17" 5.5 6.8 8 9.1 10.4 11.6 12.9 14.2 15.7 17 18.5
18" 6 7.2 8.4 9.8 11 12.4 13.6 15 16.6 18 19.6
19" 6.3 7.6 8.8 10.3 11.5 13 14.3 15.8 17.4 18.9 20.6
20" 6.7 8 9.4 10.8 12.1 13.7 15.1 16.8 18.4 20 21.7
21" 7.1 8.4 9.8 11.3 12.8 14.5 16 17.6 19.3 21 22.8
22" 7.4 8.8 10.4 12 13.4 15 16.8 18.4 20.2 22 24
23" 7.7 9.2 10.8 12.5 14 15.6 17.5 19.2 21 23 25
24" 8 9.6 11.2 13 14.6 16.4 18.2 20.2 22 24 26.1
25" 8.3 10 11.6 13.5 15.2 17 18.9 21 22.9 25 27.3
26" 8.6 10.4 12.2 14 16 17.8 19.8 21.8 23.8 26 28.2

Fig. 3: inches of pitch for each blade angle and propeller diameter.

Setting Bolts

Blade angle Right: fwd bore "R" Right: rev bore "L" Left: fwd bore "L" Left: rev bore "R"
16° 16 1 16 1
18° 18 18
20° 20 2 20 2
22° 22 22
24° 24 3 24 3

How It Works

  • Two threaded bores in the body, marked "R" and "L", each hold a stop bolt.
  • Right-hand prop: forward pitch is set by the bolt in bore "R". Left-hand prop: by the bolt in bore "L".
  • Example: bolt #20 forward and #2 reverse gives 20 degrees in forward and in reverse.
  • 1 millimeter of bolt length changes blade angle by 2 degrees.
  • Rotation is seen from the stern looking forward, engine in forward: clockwise = right hand "R".

Changing the Rotation

  • Put the prop in the feathered position; undo the zinc screws and remove the zinc.
  • Undo the nut locking screws and remove the nut.
  • Remove the circlip on the aft edge of the hub.
  • With the prop still feathered, release the zinc-bearing ring.
  • One aft tooth of the hub carries a reference mark; the ring has one tooth marked "L" and one "R".
  • Refit the ring with the "L" tooth on the mark for left-hand rotation, or the "R" tooth for right-hand.
  • Refit the circlip, tighten and lock the nut, refit the zinc with its 3 screws.
  • Swap the pitch setting bolts to suit the new rotation.

Feathering

  • Motor at 2 to 3 knots in forward, then kill the engine still in forward gear: a well-greased prop feathers as soon as the shaft stops.
  • Never stop the engine in reverse: the blades stay in reverse and cannot feather (can be used to drive a shaft alternator).
  • Mechanical gearbox: stop the shaft by engaging reverse, only after the engine has stopped completely.
  • Hydraulic gearbox: shut down in forward; residual pressure locks the shaft long enough to feather.

Warnings

  • Do not shift forward to reverse (or back) with the engine at high RPM.
  • Idle down and shift at low RPM to avoid shock loads on the blade gears and cone gear teeth.

Maintenance and Removal

Maintenance

  • Keep the body completely full of the recommended grease; re-grease at least once a year.
  • Replace the zincs at least once a year, even if they still look OK; add a shaft zinc where possible.
  • Clean the contact faces between zinc and prop / shaft when replacing.

Removal

  • Remove the zinc and the nut.
  • Fit a long-armed gear puller over the front of the propeller and tighten its centre bolt (Fig. 7).
  • If the puller bolt cannot reach the shaft end, loosen the Max-Prop nut and leave it on: the puller pushes on the back of the nut.

Fitting a New Locking Nut

  • A new propeller comes with its nut already machined to fit.
  • Standard nut (Fig. 8): when locked on the shaft it must bear on the three surfaces S1, S2, S3. Lengths L1 and L2 must match the hub exactly; L3 must exceed the threaded length of the shaft end.
  • Check with a thin coat of Prussian blue on S1, S2, S3: turn the nut lightly in its seat; all three hub surfaces must come up blue.
  • The shaft thread must not touch the threaded end of the nut, and blade rotation must not stiffen when the nut is tight. If it does, take a very small amount off S1 with a flat smooth file.
  • Sail drive nut with anti-shock device (Fig. 9): bears ONLY on S1 and S2 and is secured by 2 threaded pins plus a central screw with a dowel.

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