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Frequently Asked Questions

How is my propeller and estimated performance calculated?

All the data that you provide on our Henleys specification sheet is entered into either two or four separate propulsion packages. The resulting size is then designed with CAD to American Bureau of Shipping standards and pitched to ISO484/2 Class 1 or 2 standards. NOTE: The information that you supply on our specification sheet is critical to the predicted propeller size and estimated performance / engine load.

Will these design packages give a defined result in performance and engine load?

NO!  This is not possible as the number of endless combinations of vessel design.. applied BHP and reductions make it impossible for a design program to quantify.

Will tank testing the design help with defining performance?

Yes - this is the best method known to closely define performance at the DESIGN STAGE!  The next problem is that the vessel must be built exactly to the design specification, as again all predictions will fall wide of the mark if say the vessel is overweight or does not achieve correct designed trim when in use.

Are all propellers the same?

No – different configurations from various suppliers will give varying performance results –  in most cases our own designs have given outstanding results on the majority of applications BUT there have been instances where other makes / designs have suited a particular style of craft better.  The unfortunate part of this is that "discovery" is made through trial and error and one cannot purchase a “custom built” propeller from Henleys on a trial and buy situation!

Should I have my vessel weighed while under construction?

Yes – vessel displacement is critical to vessel performance and engine load.  Most engine makes now require that maximum loaded RPM is set within a 20 to 50 margin on engine RPM which equals a target of approximately 1.5%, yet a lot of vessels do not achieve the correct trial weight specified - being as much as 10 to 30% out!  Note: Engine suppliers can have a 3 to 5% variance on power supplied - including latest electronic motors! This will affect achieved performance and rpm. This can only be discovered on sea trial with the engines being fully tested.

Will I get any form of performance guarantee with the purchase of my propeller?

No – due to above stated variables it is not possible for us to guarantee something that we cannot truly define.  A vessel's performance is locked into the vessel's design and final form – A PROPELLER IS NOT A MAGIC WAND!  We use our past experiences to provide as accurate as possible performance estimates, which are based on the information you supply

What form of warranty do I get?

Henleys will warrant the products supplied, for 12 months from date of purchase, to be of merchantable quality and that they meet the international pitching standard of ISO484/2 Class 1 for 'Barracuda', 'Tiger' and 'Black Tip' designs – all others are pitched to ISO484/2 Class 2 standard.

What happens if on trial the engine loaded maximum RPM is not to the manufacturer’s specifications?

The propellers will need to be adjusted (if possible) – generally in the order of pitch, cup, and diameter or blade area.

Who pays for this work?

The Boat owner. In the majority of cases one re-pitch is sufficient, but as the programs used to calculate the adjustment are generic only, in some cases the client may need to repeat the process.  ALL relating extra costs i.e. loss of chargeable hours, haulage, removal, freight and re-installation are the owners care!

What causes a vibration?

In most cases it is bent shafts, engine alignment to drive train when the vessel is in service or the machinery supplied has not been fitted correctly as per instructions supplied.

What about vibration in relation to my propeller?

Henleys will guarantee that their propellers achieve a static balance at time of manufacture.  This is a universally accepted tolerance and is sufficient for 99% of product supplied; however some vessels are more susceptible to panel vibration.  This becomes apparent after a sea trial and the first best option that we have found is to have the propeller dynamic balanced which 99% of the time improves or rectifies the situation.  Any costs involved in dynamic balancing are the owner's care.

What happens if there is a vibration?

Henleys do not accept any responsibility for vibration levels on sea trial as the resulting combinations of machinery and vessel make it impossible to pre-define a level of tolerance unless an in-depth design study and TVA is undertaken by the client before any equipment is fitted to the vessel.

Can galvanic reaction affect my propeller and stern gear?

YES – all propellers (including Stainless Steel) and stern gear are susceptible.  It is the owner’s total responsibility to ensure his bonding system is adequate for total protection at all times. Henley’s certificate, supplied with every new propeller, includes a full material specification and batch number. There are well known EXPERTS in this field – please ask for their contact details if you are not sure.

How important is the installation of stern gear?

The correct installation of your drive train equipment is CRITICAL to the final result.   Henleys experience is that over 98% of problems realized on sea trial are the direct result of incorrectly installed engines, gearboxes, drive shafts, stern gear, propellers.  Henleys have taken this area very seriously and provide full installation instructions with every new propeller purchased. We also supply full installations of drive train equipment, available on request to suit each individual situation

How can we ensure the propeller will fit the shaft and key?

If Henleys supply the propeller and shaft then in approximately 90% of cases the two are fitted (lapped and blued) in our workshop to ensure an 85% to 100% fit is achieved.  For approximately 10% of our work the shaft is not in our shop at the time of propeller completion - it then becomes the responsibility of the vessel's engineer to lap and blue on site (at the owners cost).  Please see propeller fitting instructions.  If the shaft is machined by another company Henleys do not accept any responsibility for fit based on given dimensions or a drawing.  However, Henleys will ensure an 85% to 100% fit is achieved to a supplied and tapered mandrel that is an exact copy of the finished shaft taper.  The above also applies to the forward end of the shaft taper and coupling.

Why is an anti – singing edge required on some propellers?

In our experience a “singing” prop occurs approx. 4 in every 100 propellers. It can affect any craft from small cruisers to large ships, in new or recently refurbished existing propellers or drive train equipment. In twin installations it can be one or both of a matched pair. Ever run your finger around the edge of a wine glass? Depending on the amount of fluid in the glass and on your finger one can get varying degrees of harmonics. The same can apply with a propeller and drive train when rotating at any rpm through the range. In most cases the rpm bands are only small say 50 rpm but they can go as far as 400 before it is outside a certain frequency that we can hear. The same propeller, which meets all industry design parameters, can be placed on another vessel without the same problem occurring.

Why can’t anti singing edges be applied to all propellers from new?

They can but it would not prevent harmonics occurring as a propeller manufacturer has no way of defining if there will be a problem or at what rpm band it may become audible. The anti-singing edge is only applied after a sea trial uncovers the problem in an effort to change the frequency. In most cases the problem is sorted out first time but in some vessels the anti-singing edge simply moves the band up or down, shorter or wider.

Who pays for this work?

This is a matter of trial and error to custom match the prop (easiest item to alter in the drive train) to a particular vessel – there is no other way of defining a result so the costs fall on the owner.

Will the noise experienced damage my propeller?

NO – it is just annoying if one cannot drive through the band quickly.


The team at Henleys are happy to manufacture your designs 


The Henleys team are fully qualified to fabricate parts for all boating needs


Operating for over 95 years you will receive the highest quality
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