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Teleflex Helm Pump Seal Replacement

This article is an illustrated tutorial on replacement of the main shaft seal in a Teleflex helm pump used in hydraulic steering systems on Boston Whaler boats.

Teleflex Hydraulic Steering

Many Boston Whaler boats are equipped with hydraulic steering using components made by the Teleflex company. A common problem is leakage of hydraulic fluid from the helm pump. This usually occurs from the main front shaft seal. The replacement of this seal is straightforward, and can be easily accomplished. Replacement of this seal often cures most problems of hydraulic fluid leakage from the helm pump.

A recent survey of four Boston Whaler boats from c.1988-1990 showed all four had leaks at the helm pump. In all cases, replacement of the front main shaft seal cured the leak.

Hydraulic fluid is extremely low viscosity, and it will flow with amazing ability. Typically the leak occurs at the bottom of the front shaft seal. Fluid will flow from this point, down the forward surface of the helm pump, back to the base, and onto the console. From there the fluid will flow to the deck, eventually showing up at the base of the console. The fluid can cover an amazing distance, and it may show up far from the actual source of the leak. Careful inspection will usually reveal the source of the leak to be at the main front shaft seal.

To replace this seal, the steering wheel must be removed. A small set screw holds the plastic or wood center hub cover in place. Loosen the set screw and remove the hub cover to reveal the retaining nut beneath it. Remove the retaining nut. Pull the steering wheel from the shaft using a gear puller. A sequence of illustrations shows this process below:

 

[Photo: Grant Six-Spoke Steering Wheel on Boston Whaler helm]
Grant Six–Spoke Steering Wheel
Most Boston Whaler boats are equipped with a Grant stainless steel steering wheel with five or six spokes. The center plastic hub cover is retained by a small set screw.
Photo Credit: JWH.

 

 

[Photo: Retaining nut on Steering Wheel]
Retaining Nut
After the hub cover is removed, the retaining nut is revealed. Remove the retaining nut from the shaft.
Photo Credit: JWH.

 

 

[Photo: Gear puller ready to remove wheel]
Removing Steering Wheel
The steerting wheel is tightly seated on a tapered and keyed shaft. It may be necessary to use a gear puller to pop the wheel off the shaft. Typically just a slight amount of force will break the wheel loose.
Photo Credit: JWH.

 

After the wheel has been removed, you will see the front shaft seal cover plate. This is a circular plate which is retained by three phillips-head screws. Remove the plate. If the helm pump is full of hydraulic fluid, there typically will be some fluid retained behind the cover plate. If the helm pump has been leaking for a long time, the fluid level will probably be down to the point where the shaft seal leak is above the fluid level, that is, the fluid has already leaked out via this path. Have a rag ready to wipe up any fluid that comes out.

 

[Photo: Close-up of helm pump showing seal cover plate in place]
Helm Pump Seal Cover Plate
The front shaft seal cover plate is retained with three small phillips-head screws; two have already been removed.
Photo Credit: JWH.

 

After the shaft seal cover plate is removed, the front shaft seal will be visible. At this point you can assess the diameter of the shaft and seal. There are two versions of this pump in common use with Boston Whalers. One has a 0.75-inch diameter shaft and the other has a 1.0-inch diameter shaft. According to Teleflex, the usage of these seals was as follows:

The easiest way to tell which seal you need is just to measure the old one. You can do this while it is still in place, as a difference of 0.25-inch in diameter should be readily apparent.

 

[Photo: Close-up of helm pump showing seal cover plate removed]
Front Shaft Seal
The helm pump shown here is the 1.00-inch diameter shaft and is installed on a 1990 Boston Whaler boat. The helm was probably made c.1989.
Photo Credit: JWH.

 

Carefully remove the old seal from its seat. A safety pin makes a good tool for picking the seal from its seat on the shaft. Poke the pick into the seal between the inner and outer surfaces on the exposed face, and gently lift it from its seat on the shaft. Be careful not to scratch or damage the shaft, the facing of the pump, or the seal seat.

 

[Photo: Close-up of helm pump showing seal]
Removal of Front Shaft Seal
Here, an old dental pic is used to pry the seal out. A safety pin works better.
Photo Credit: JWH.

 

 

[Photo: Close-up of removed seal]
Front Shaft Seal
This is an old front shaft seal, now removed. It appears to be in good condition but it leaked profusely.
Photo Credit: JWH.

 

The seal is not an O-ring, but rather a quad-ring. There are two surfaces on both the outer and inner diameters which form a seal. In an emergency, you might try an O-ring. I found one in a helm pump that was leaking, but it apparently had worked for some time before failing. Get the proper seal replacement part to do the job right.

 

[Photo: Close-up of removed seal]
Quad Ring Seal
Both inner and outer surfaces of the seal have a concavity. This is called a quad O-ring.
Photo Credit: JWH.

 

A good local hardware store may be able to supply the quad O-rings. The larger diameter seal is believed to be a "dash 214 quad O-ring" according to the Aerospace Standard 568 published by the Society of Automotive Engineers. The smaller diameter seal is believed to be an AS568 standard "dash 210 quad O-ring." These typically sell for less than a dollar and are made from Buena-N (nitrile rubber) material that should work fine as a seal. You can also source these quad O-rings from a larger vendor like McMaster-Carr. A package of 100 is less than $15. Thanks to David Thickens for information about the standard ASE dash numbers for the O-ring dimensions and the McMaster-Car part number. Again, be sure to get quad O-rings, not round ones.

If you cannot find a replacement quad O-ring from a hardware supplier, you can buy a replacement part from Teleflex through their many resellers. A Teleflex replacement part will typically cost $5 or more.

After removing the old seal, clean any debris from the seat around the shaft and install the new seal. Replace the seal cover plate. Re-install the steering wheel. Re-fill the helm pump with fluid to the proper level. Do not over fill. If you are using a side-mount cylinder, the fill level must be set when the ram is retracted, i.e., when the wheel is turned hard left. This is because of the asymmetrical nature of the ram; it has unequal volumes of fluid. If you fill the helm pump on a cold day, allow for some expansion of the fluid on hotter days. If your helm pump is mounted on an upward angle (typical), the proper level for the fluid is about 0.25-inch below the bottom of the filler. If the helm pump is mounted perfectly level, the proper level is even with the bottom of the filler.

 

[Photo: Close-up of removed seal against ruler for size measurement]
Quad Ring Seal
There are two sizes of main shafts, and two sizes of seals. The smaller shaft uses a seal with an inner diameter of 0.75-inches, show here.
Photo Credit: JWH.

 

 

[Photo: Close-up of removed seal against ruler for size measurement]
Quad Ring Seal
The larger shaft uses a seal with a 1.0-inch inner diameter, shown here.
Photo Credit: JWH.

 

Helm Pump Filler Cap

There are two styles of filler cap, vented and non-vented. Teleflex now recommends using a vented filler cap, but it is often seen that older Boston Whaler boats are equipped with a Teleflex helm with a non-vented filler cap. This can be the cause of some of the leakage problems. In warm weather and in direct sun, the temperture of the fluid can rise, and the fluid expands. If the helm pump filler is tightly sealed and non-venting, this expanding fluid can exert a lot of force on the shaft seal, possibly leading to leaks. The vented cap is Teleflex P/N HA5431.

Comments or Questions

If you have a comment or question about this article, please post it in the message thread reserved for this purpose in the Whaler Forum.

Additional Reading

The Teleflex website provides a wonderful on-line resource of information about their products.


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Last modified: Saturday, 23-May-2009 23:39:02 EDT
Author: James W. Hebert
This article first appeared July 10, 2004.