Prop Protector Installation

The diagram above illustrates the components associated with the selection and installation of all types of Prop Protector. Although the diagram shows one type of stern shaft bearing, the following notes apply equally to craft fitted with either P or A struts or brackets.

In most installations, the gap between the propeller hub and the shaft bearing is wide enough to allow the installation of a Prop Protector. This gap must be sufficiently wide to accommodate the cutter plus an additional gap of 6mm (1/4 inch) between the Protector and the bearing. Extra Large cutters need a gap of approximately 12mm (1/2 inch).

This extra gap is necessary to allow water to circulate to the shaft bearing for cooling and lubrication. It also allows for any end float on the prop shaft. If there is excessive end float due to gearbox end play or over-flexible engine mounts, this extra movement has to be provided for. The recommended gaps for all types of Prop Protector are shown in the specifications. If the gap on your shaft is inadequate, it can be increased by any of the following methods:

1. For adjustments of between 2mm (0.08 inch) and 5mm (0.2 inch), it may be possible to disconnect the prop shaft from the prop shaft coupling, move the shaft aft by the required amount and re-tighten the connection. If this method is used it is important to ensure that there is still sufficient engagement between the shaft and coupling to maintain a secure connection under full power.

2. For larger adjustments, a coupling spacer or a flexible coupling may be fitted between the coupling and the gearbox flange.

We can now supply coupling spacers for most of the popular gearboxes ‘off the shelf’. See order page for further details. We can also arrange for the supply of spacers for gearboxes not listed. Please allow three weeks for delivery and supply full details of your engine and gearbox.

Underwater Installation

One of the unique features of Prop Protectors is that they can be installed with the vessel afloat.

The fasteners supplied for installation of ALL Prop Protectors have a nylon coating which serves as a self-locking mechanism and can be re-used twice.

If in doubt, please telephone us on +44 (0)286 8658839 for advice.


What’s in the box?

All Prop Protectors are supplied with self locking A4 stainless steel fastenings, allen keys, and installation instructions. Both types are easy to install. For instance, the Clamp-On cutters can be installed in as little as ten minutes.


Additional Considerations

Other factors to consider when selecting the correct Prop Protector for your vessel

1. The diameter of the cutter blade must be larger than the diameter of the propeller hub and of the bearing housing in the strut of stern tube. If the blade is shielded by either of these, it cannot cut entangled line. The overlap of the blade should be at least 6mm (1/4 inch).

2. The minimum gap specified for each type and size of cutter should be of UNTAPERED shaft. If all or part of the gap consists of tapered shaft, a cutter for a slightly smaller shaft diameter should be selected so that it can then be machined to match the taper of the shaft.

3. Prop Protectors may be installed with the vessel afloat using the nylon coated fasteners supplied with all Prop Protectors.