Kiwiprops™

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Mounting on Shaft

This section is also available in the   OPERATING MANUAL

Before fitting your new Kiwiprop™ to a shaft - first check that the shaft is free to rotate and can be spun easily by hand to ensure correct feathering.

Remove the nut with 1/2" square drive from the internal recess in the aft section of the Boss of the propeller by releasing the 2 x M8 locking set screws.

Check the fitting of the nut prior to finally mounting the propeller with key by ensuring the nut will freely screw right down the thread.

The front face of the nut must come very close to the small end of the taper. This will ensure the nut can subsequently push the rear face of the boss tightly onto the taper when mounted.  Remove any burrs or impediments to the smooth operation of the nut.  Smear the thread with a marine grease.

Remove the key from the keyway on the shaft to enable correct mounting checks.

To ensure the key is sized correctly, mount the unit without the key, to ensure the taper is tight, marking the front face position on the shaft with an indelible pencil, and then again with the key to ensure it is not binding on the keyway which can then  be ground down if required.

This will show as the boss not returning to the same position as marked previously required - an indication that the key is binding  and preventing the taper seating correctly.

This can be caused by insufficient depth in the keyway recess that has been milled into the shaft.  The outer face of the key should have clearance and not be touching the matching outer recessed  face of the boss.

Check that the boss is tight on the shaft taper without any lateral movement even when pushed only lightly up the taper.

The boss will need to be lapped carefully with grinding paste to ensure a neat fit if this is not the case.

The unit must fit exactly with a neat fit to the taper and zero clearances on the taper surfaces.

Mark the front face of the propeller on the taper in each case.

All   SAE  1.125”   1.250”  1.500" and ISO  40 mm units mount with the front face 0.250”  0.625” and 30 and 20 mm respectively down from the taper start.  This allows for common boss sizes.

Nuts on SAE 1.250” shafts protrude ~ 1⁄2” aft to allow for the fit of the spigot extension on SAE standard shafts.

Wipe all mating surfaces clean and lightly smear with a marine grease including both keyways. Check that the taper length will allow the nut to pull the propeller tight on to the shaft. In all cases the rear internal face of the boss should protrude ~ 1⁄4” or 6 mm aft of the small end of the taper, which is the SAE and  ISO standard, to ensure the nut pulls up on the boss correctly and doesn’t first bind on the thread giving only the appearance of correct mounting.  Larger 1.500"  35 and 40 mm shafts will have a pull up of 10 mm.

Failure to tighten the boss onto the taper and key with the nut will result in a loose mounting with subsequent shearing the key and loss of the entire propeller.

A new key will be supplied for all 1 1⁄4” shafts with one face ground down by 0.030” which allows for a common boss size.

Ensure the ground face is mounted outwards. Always replace any key that is old or shows any signs of corrosion.

Keys are usually only a brass and can and will corrode rapidly in high corrosion environments. The shearing of a corroded key will result in the automatic loss of your new propeller.

NB: The key must not protrude aft past the small end of the taper where it will interfere with the nut and create the illusion of correctly pulling the boss onto the taper.

Finally, insert the key and mount the boss on the taper.

Tighten the square drive attachment nut torqued to ~  20 ft lbs  or 27 Nm

Apply Loctite™ to the threads on the two M8 locking screws and tighten these home using  ~ 1 ft lb  or  1.4  Nm of torque.

These will then lock the nut to the boss.

When these instructions are followed correctly the propeller will remain securely mounted into the future as long as the key retains it's integrity.