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How to Install Marine Bearing Seal

by | Dec 2, 2018 | Technical Guides | 2 comments

Easy Steps to Install a Marine Bearing Seal Correctly

Grease is applied to a marine seal and bearing for one reason only, to reduce friction. Friction produces heat, excess heat through incorrect installation destroys bearings.

Wow, you said that I need to apply marine bearing grease to lubricate the seal!

Is it true, poor installation practices reduce the life of bearings by up to 40%.

Australian Marine Bearing Seals

Rubber marine seal and stainless outer ring

Firstly, apply grease to the Australian marine seal significantly reduces heat-causing friction. Surprised?

Secondly, the ID of a Marine grease seal is a shrink-fit and very tight fit on an axle.

Thirdly, the ID of a marine seal does not spin, only the steel OD of this seal spins.

The connection between the rubber seal and stainless metal housing creates friction.

There are two lips on the inside of the rubber seal. Apply ample grease to these lips to significantly reduce friction and greatly increase bearing life.

As a result, water ingress does not continue to be a significant problem.

In 90% of cases, marine grease is not applied to the inner lip of a marine seal. Grease prevents air from being sucked into the bearing cavity when the hot wheel hub is immersed into the cold seawater.

A greased marine seal provides an additional barrier to help prevent water ingress. It also offers corrosion protection.

Oil Seal

Proper installation of any seal requires lubrication on the machined steel surface.

Couplemate sells NSK bearing kits and seals.

Bearing Buddies

Can the over-lubrication of bearings by boaties fix the problem of water in the grease? How?

New grease pushes out the old marine bearing grease through the back grease seal.

axle JackThis method is dangerous and should be avoided.

  1. The ideal amount of grease in your bearing cavity is approximately 50%.
  2. As the bearing cavity heats up, excess grease spills over the inside of your wheel.
  3. Excess grease is ‘flung’ onto the road surface during transit.
  4. Grease stains on the springs, wheel rims and undercarriage of your boat trailer are almost impossible to clean.

Inspect every bearing set for carbon black in the grease, then correct adjustment.

On one occasion at the Hawkesbury River, I was preparing my boat for the return home to Brisbane. While checking the bearings, I found one bearing journal so worn that it would not have successfully made the trip back.

Disaster saved, from checking my bearings before the long trip home.

Frequent Bearing Checks

Increasing the frequency bearing checks reduces disasters.

Over time, the outside casting on your bearing wears. This wear creates carbon black. As a result, worn bearings also cause heat and accelerates bearing failure.

Are your bearing buddies being stolen? Maybe they are not being taken, find how why.

Please leave a comment if you found the above tips useful. If you find errors or disagree, I would love to hear from you.

Finally, here is another good article on why caravan and boat bearings fail.


  1. BoatMate Trailer

    What a great site, glad I found you. You’ve already provided some great advice!

  2. Alan Murrie

    While checking the bearings, I found (on) ONE bearing journal so worn; it would not have successfully make the trip back.
    I guarantee you bearing failure IF you expect your bearings to last forever and ignore critical checks.


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