Yes. We have had many decades of replacing stuffing boxes and mechanical type face seals with our lip seal designs since 1984. There are a number of ways of doing this. Please contact KSS Ltd for Technical support and options.

No. By nature of design – if fitted correctly as per instructions the KSS will not cause any vibration problems – in fact with the forward bearing in place the engineer is forced to achieve correct alignment between engine and drive train so the installation runs smoother with the install of the KSS system.

Some of our earlier stuffing boxes have been in vessels for over 30 years however these were invariably on the traditional low powered, low rpm installations. With the application of modern, lightweight, soft mounted engines the stuffing box life span is greatly reduced as the white metal bearing wears, the owner tightens the packing and applies more and more grease (KSS does NOT USE ANY GREASE). This process can peak at approx 1000 hours depending on the installation. Not only does the stuffing box wear but it is also creating significant wear on the propeller shaft during this process – of course this wear factor varies from vessel to vessel. We would expect the KSS to achieve 5000 + hours without any issues if fitted and operated as per instructions. In most vessels this represents 10 to 40 years of use.

NO – the design of the KSS allows for all wearing parts to be replaced at a price that becomes the obvious choice rather than buying a new Shaft Seal. If one is considering refurbishing a KSS it can only be done at our KSS factory to ensure that all build tolerances and process is to standard.

NO – the KSS is designed to be used over the life span of the vessel without ever needing replacement.

NO – the KSS seal is custom built in that each seal has a unique build number (not batch) so all components, process and testing can be tracked and verified over the life time of the shaft seal. To our knowledge no other seal Worldwide can provide this level of scrutiny and security that ensures a product built to the highest standards possible.

All of the KSS supplied are double clamped at each end. Two onto the stern tube and two on to the shaft seal itself. Various shaft seals Worldwide use the standard hose clamps that we use to suit 1” to 2” KSS. This system of attachment has never failed in any seal to our knowledge. We take an extra precaution with the KSS from 2.25” upwards as we have applied a unique system of using Bolted SS clamps as an extra safe guard. This system is full proof if fitted correctly and has not been matched by our competitors.

How long is a piece of string? Modern shaft seals of many designs are replacing old stuffing boxes to reduce ongoing maintenance and wear and tear. We cannot state how we compare with stuffing boxes and other more modern shaft seals however we believe we are priced in the middle of our competitors who market modern shaft seals. This question sits at #4 on list of importance from our customer surveys and as we point out why save a few hundred dollars while putting you and your crew at risk.

From the OWNERS point of view they will not have to adjust packing, apply grease, suffer from excessive shaft wear, experience continuous water flow into the vessel to lubricate the shaft packing, or excessive amounts of grease into the boat for those who do not understand how a packing gland and some grease based lip seal designs actually work. The issues associated with mechanical type seals that we address with the KSS are explained in the KSS “History” document.

KSS main competitors on the worldwide market are the PSS shaft seal from the USA, Tides from the USA and the Deep Sea Seal from the UK. All these shaft seals have strengths and weaknesses. We address these in the KSS “History” document. KSS can also provide specific issues presented by these competitors’ seals and also explain why the KSS is a more robust system.

This will vary from boat to boat. Most have an existing stern tube OD that matches our existing KSS hose ID. If we are replacing a packing gland then we can forward you a set of instructions on request.

The advantage is that one ensures the propeller shaft is then placed in the center of the stern tube and the Centre of the KSS which significantly reduces vibration, wear and tear on many associated drive train components – including the gearbox. In most cases this will mean that the engine alignment will need to be re set to be in true alignment with the propeller shaft.

Some of our commercial customers have over 8000 hours without any lip seal wear. This equates too approx. 40 years in a pleasure craft. If the seal position is compromised due to wear simply reduce hose length by ½” to seat on new shaft surface.

We have intermittently run our lip seals dry until the KSS nose is too hot to touch and still achieved over 195 engine hours without leaking! Please ask for test paper #4.
Yes. We have had many decades of replacing stuffing boxes and mechanical type face seals with our lip seal designs since 1984. There are a number of ways of doing this. Please contact KSS Ltd for Technical support and options.

There is no doubt that shaft grades play a significant factor in lip seal grooving of shafts. A bronze or 316ss shaft will show lip seal groves in approx. 3000 hours. To date modern 2205ss and AQ17, 19 and 22 have not shown any grooving from contact of KSS seals and shaft surface.

KSS Market research into customer needs in relation to shaft glands and seals is extensive. The results of our on-going R&D are seen in the seven points listed on THE BACK of our KSS Brochure. If you wish to do your own we suggest that you present the “seven points to consider when purchasing a shaft seal” to yourself OR trade clients and record their response in order of preference / importance. Once a personal level of requirements has been established the same order of preference can be applied to other seal options to see which option is best for a particular vessel.


The original fixed driveline and engine system has been around for over 100 years.

It consisted of a shaft made from bronze that was generally supported by a bronze strut with bearing aft, an out board bronze bearing housing that was threaded on to a 10g copper tube, an inboard bronze packing gland that was threaded onto the internal end of the same copper tube.

The Bronze Packing Gland generally had a white metal bearing that was used to centralise the shaft in the tube, bearings and packing gland which relied on hemp packing that could be adjusted by a bronze “follower”. If adjusted correctly the system allowed just enough water into the vessel to keep the white metal lined gland cool when in operation – Yes they were designed to leak!

Forward of the packing Gland system we had a shaft half coupling that was directly bolted onto the gearbox output flange. The gearbox was direct coupled to the engine. The engine was solid mounted (generally shimmed in place) to the vessels engine beds.

The Static system applied to the driveline and engine / gearbox package achieved simplicity and longevity in its day. The system ensured that all rotating components remained in line regardless of the significant loads placed on a large mass of steel sitting in one’s bilge (engine and gearbox) due to propeller thrust and ship role and yawl due to wind and seaway conditions.

This system was applied to most vessels World-wide up until the 70’s and in its day provided (in most cases) a safe, reliable and efficient drive train / engine package giving many thousands of hours of motoring in various applications.

What went wrong?

In most cases the wear and tear issues arose from the packing gland being adjusted too tight which resulted in excessive heating of the white metal to melting point (causing the shaft to seize). The natural action of the packing material tended to wear grooves into the bronze shaft material so over time the shaft and white metal required replacing.

Construction of vessels at that time allowed the vessel keel line to “hog” over the vessels life – some vessels were stiffer than others but most cases resulted in this fate resulting in the driveline running in a system that was no longer “in line” which added to the wear of components.

Due to the construction methods and materials used at the time most vessels ran to an acceptable level of smoothness and Db. levels. Vibration was generally a result of misalignment, poor propeller design and a solid mounted engine directly bolted to the engine beds. This is not to say that some modern systems applied today give any less vibration or grief.

Why did we change?

Some designers / engineers view the change in applied driveline types being due to a few small components such as Mechanical type shaft seal or a flexible coupling being inserted into the overall driveline package. In most cases the simple addition of the said components has created all sorts of problems in safety, noise, vibration, performance and longevity.

The changes (which are still evolving) applied to the install of a driveline package are due to a number of significant factors such as:

  • 1.Marine engine’s supplied with industrial type rubber mounts that have no relation to the actual applied thrust.
  • 2.Changes to materials and methods of vessel construction resulting in stiffer hulls and superstructure.
  • 3.Production boatbuilding for the pleasure market which demands cost effective methods in all facets of a vessels build time.
  • 4.The application of larger BHP engines with significantly improved HP / weight ratios.
  • 5.Changes to hull design and applied BHP which has resulted in vessels obtaining higher velocity thereby placing added stresses to the hull and driveline components.
  • 6.A greater expectation of smoothness and low Db. Levels.
  • 7.A larger variety of gear box designs providing options in angle, configuration and mounting point in the vessel.