Page 1 of 10  > >>

Dec 20, 2016
Category: General
Posted by: alvin

The proposed gateway to a planned interoceanic canal shows little sign of activity but locals say Chinese experts have visited recently and work will start soon.

Oct 29, 2016
Category: General
Posted by: alvin

EU and 24 countries sign long-awaited agreement to protect 1.1m sq km of water in Southern Ocean, ensuring that fewer younger fish will be caught

Jul 29, 2016
Category: General
Posted by: alvin
The Utila Ferry War is Over.
Contact Info
an image
Almacen Naval
Roatan, & Puerto Cortes, Honduras, Rio Dulce, Guatemala
Contact Us
You are here: Home » Propeller Install

Propeller Install

Installation Procedures

Propeller Fit

In order to properly mate the propeller to the shaft taper, the following is one of the most commonly used methods:

  1. The taper should be coated with Prussian Blue.

  2. The propeller should then be put on the shaft without the key and gently tapped snug onto the taper.

  3. If the Prussian Blue is uniformly removed - the fit is good.

  4. If the Prussian Blue is not uniformly removed, the fit is not good. An appropriate lapping compound should then be used and the test repeated.

Since a 100% fit is not always possible, an effective seal such as waterproof grease should be used to exclude water. This seal will also protect against dissimilar metal corrosion.


Bearings, shaft and couplings shall be aligned to a tolerance of no more than 0.004 inches (0.10mm) measured between the parallel Range of the coupling

with the coupling bolts loose. Smaller shaft sizes should tum freely by hand with the clutch disengaged when the coupling bolts are drawn tight

Note: The shaft should be aligned alter the boat is in the water. Do not force the shaft to accommodate the engine bed, bearings or stuffing box.

Propeller Overhang

The distance between the forward end of the propeller hub and the aft end of the last strut bearing shall be limited to one shaft diameter.

This does not apply where the last bearing is installed aft of the propeller.

Propeller and Key Installation

The propeller should always be installed on the shaft taper first without the key, and its position marked with a pencil. The propeller is then removed, the key installed and the propeller installed so its position is at the pencil mark. This precaution will indicate if the propeller is riding the key up the key way end radius, forcing the propeller off center. Every propeller installation should be provided with a system consisting of a straight key, propeller nut, jam nut, and cotter key. Other positive-locking systems may be used if they protect against accidental loss of the propeller. The length of the key shall not be greater than dimension "X" shown in SAE Specification J-755.

Propeller Diameter vs. Shaft Diameter

The ratio of propeller diameter to shaft diameter should not exceed 15:1.Higher ratios may create excessive stresses and may shorten shaft life. High performance boats, such as racing boats, should consider a maximum ratio of 12:1.

Shaft Seals and Shaft logs

Shaft seals shall be readily accessible. Every shaft seal shall be constructed in such a manner that if the sealing element locks or freezes to the shaft, the resulting rotation of the seal will not create a condition wherein more than two gallons of water per minute can enter the hull with the shaft continuing to operate at low speed.

If a shaft seal utilizing replaceable packing material is installed in the boat, it shall have clearance along the shaft line to permit replacement of the packing without uncoupling the shaft or moving the engine. Face-seal and lip-seal types are not considered replaceable within the meaning of this paragraph.

The use of graphite-impregnated packing is not recommended because of the possibility of galvanic corrosion of the shaft material.

FEP Fluorocarbon-impregnated asbestos braid, the fibers of which are impregnated with the plastic prior to braiding, is considered to be excellent for shaft seals. Wax-impregnated flax packing may be used.

A shaft seal of the face-seal. lip-seal. "0" -ring or frictionless types shall be designed in such a manner that it can be operated at low speeds after failure of the seals without permitting more than two gallons of water per minute to enter the hull.

A boat having a stern tube or any other type of construction that tends to trap water next to the shaft shall be provided with a means of water circulation. This recommendation is to avoid the corrosive effects of stagnant water.

This is from: