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CATALOGUE

The Max-Prop feathering propeller range in one place: Easy, Easy Antishock for SailDrive, Whisper and Boomerang, with diameter and shaft ranges, how to choose the number of blades, drag and bollard pull charts, and anodes, grease and cruising kits.

DocumentMax-Prop Catalog
FormatPDF · 12 pages · 2.3 MB
LanguageEnglish
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ContentsModel SelectionPerformanceSailDrive & BoomerangAnodes & GreaseProducts
Max-Prop Catalog

What's in the Catalogue

Pages Contents
1–2 The story, foundry and machine shop; Max-Prop models through the years (1972 Original to 2018 5 Blade Boomerang)
3 Why choose a Max-Prop: reliability, efficiency forward and in reverse, drag under sail; propeller drag and bollard pull charts
4 Max-Prop models overview
5 Easy 2, 3 & 4 blade
6 Easy Antishock for SailDrive
7 Whisper 5 blade
8 Boomerang 5 blade
9 Catamaran
10 Accessories and services: anodes, grease and grease kits, cruising kits

Choosing a Model

Model Blades Diameter Shaft Best suited for
Easy, 2 blade 2 11" to 18" ¾" to 1⅛" All racing boats or smaller cruisers; very low drag under sail
Easy, 3 blade 3 12" to 26" ¾" to 1¾" 24' to 55' cruisers (medium displacement); smoother than a 2 blade
Easy, 4 blade 4 14" to 26" ¾" to 1¾" 40' to 70' cruisers (medium to heavy displacement); very smooth running
Easy Antishock for SailDrive 2, 3 and 4 14" to 20" SailDrive spline Volvo, Yanmar, TwinDisc, ZF, Sillette or Bukh legs
Whisper 5 18" to 48" 1¼" to 3½" Heavy displacement cruisers over 50 feet; large yachts 70 to 150 feet
Boomerang 5 18" to 44" 1¼" to 3" High speed vessels, electronic shift or hydraulic transmissions

As printed: the models overview gives the Easy range as 12" to 26" and the Whisper as up to 44" diameter and 3½" shafts; the detailed model pages give the figures in the table.

  • All Easy models: bolt-on installation, shipped fully assembled, externally adjustable pitch (no disassembly; can be done in or out of the water by fitting a pitch bolt of a different length). The Easy replaces the Classic.
  • Number of blades: a 2 blade has the least drag (racers, smaller cruisers); 3 and 4 blades give more power and eliminate vibrations; a 5 blade adds power and runs smoother than a 4 blade, rather than going to a larger diameter.
  • Catamarans: available in 2, 3, 4 or 5 blade versions, with models designed specifically for SailDrive; reduced drag also reduces turbulence over the rudders.

How It Works

  • A feathering propeller: it does not rely on centrifugal force to open, but on shaft torque acting on a differential-type gear in the body, so it opens immediately in forward and in reverse.
  • Forward: a well chosen diameter, pitch and number of blades usually achieves 96% or better efficiency compared to a fixed blade propeller; the maximum 4% drop is only seen at maximum throttle.
  • Reverse: the blades use the same leading edge and pitch as in forward, so power is the same in both directions; they switch in only ¾ of a shaft rotation.
  • Under sail: Max-Prop quotes 10% to 15% more sailing speed than a fixed blade propeller, most noticeable in light air. Drag depends on blade count, shaft angle and propeller location: a 2 blade on a horizontal shaft (SailDrive) has the least, a 5 blade on a high angle shaft the most.

Drag & Bollard Pull

Max-Prop propeller drag versus boat speed for 2 to 5 blade Max-Prop and a fixed 3 blade, and bollard pull for a 50 HP engine with an 18 inch propeller

Bollard pull chart: in kg, engine 50 HP, propeller diameter 18".

Easy Antishock for SailDrive

  • SailDrives need a spline attachment instead of a taper.
  • The gears in the leg cannot take the shock loads of a low drag propeller opening, so every SailDrive propeller needs a dampening device in the hub.
  • The Easy Antishock has an internal dampening device on every unit; it installs like a fixed blade propeller and has externally adjustable pitch.

Boomerang (spring assisted)

  • Hydraulic and electronic shift transmissions put almost no drag on the shaft with the engine stopped, so there is no mechanical way to stop the shaft freewheeling.
  • A patented radial spring in the body forces the blades back to feathered as soon as no torque is applied: with the engine in idle or shut down they feather within seconds, regardless of shaft rotation or boat speed.
  • Maintains the feathered position in high speed, turbulent operation.

Anodes, Grease and Kits

  • Anodes: a sacrificial anode is critical for a long propeller life. Max-Prop anodes are cast with a strong metal ring that helps disperse current loads. Aluminum anodes are available on request where zinc is restricted.
  • Grease: grease yearly at a minimum, through the pair of grease ports on the hub using zerc fittings and a grease gun, out of the water or in the water by a diver.
  • Greasing kit: grease, a grease gun, and a few spare screws and zerc fittings. The grease is also sold on its own.
  • Cruising kit ("Combo kit"): a year or more supply of parts for long distance cruisers: grease, zinc anodes and screws.

Need a part that isn't listed? Ask us to source it and quote the part number from the PDF.

Products in this Selection Guide