How To Change Outboard Prop Shaft Seals, The Easiest Way!


Blowing up a lower unit is a horrible experience, when you have to pay for it! Especially if you don’t have any warranty. So changing the gear lube periodically can help prevent this but what do you do when your prop shaft seals are leaking?

How To Change Outboard Prop Shaft Seals? Prop shaft seals are changed by pulling the bearing carrier & pushing the old seals out. Then pressing in the new seals & reinstalling the carrier. You can also pull the seals out without pulling the carrier to change them.

Here is a step by step guide to change them, as well as some tips & tricks to getting them to seal if you run into problems!

What Type Of Lower Unit Do You Have?

Changing the prop shaft seals will vary depending upon what brand of lower unit you have. Some gear cases you will be able to change the prop shaft without taking out the bearing carrier.

But then there are other gear cases that you will have to pull out the bearing carrier in order to change out the seals.

It’s important to figure out if they need to be changed or not first. The first clue to whether they need to be changed out or not. It is the color of the gear lube! (Here is an article that we wrote that will explain all the different colors you could see and what they mean!)

If you have discovered that there is a leak. Then you will need to pressure test the gear case. This will tell you where the leak is.

There are three main sources for a gear case leak. They are the shift shaft, the driveshaft, and the prop shaft.

Removing The Seals Without Pulling The Carrier

In order to remove the seals without removing the carrier. We can utilize two different methods of pulling the seals.

The first method is a common method that uses a drywall screw or self-tapping screw. As well as a small drill bit.

You can drill a hole on each side of the seal from the outside. Then take a screw and screw it into the seal so that there is a screw on both sides of the seal.

Once the screws are in, we’ll take to pry bars and pry up evenly on the two screws to pull the seal up and out!

Be extremely careful here because you can scratch the prop shaft with the screw and destroy it!

The next method is to take a flat head screwdriver and bend the outside of the seal in at four locations around the seal. Once the sides are bent in. You will be able to take a seal puller tool and work the seal up from the sides.

This method is probably safer but still has the potential for damage. It’s important to be careful will utilizing both of these engines! So, you’ve been warned 😉 Here is a video displaying the use of both of these methods:

Mercury

Mercury Marine gear cases have a mixed ratio of lower units. Some of them require you to pull the bearing carrier in order to change out the prop shaft seals. Then the other half you can change them without pulling the carrier.

For the gear cases that you have to pull the carrier on. You will need to push the locking tab down from the spanner nut on the gear case. Then you will need to remove the spanner nut. Sometimes these can be tricky and you might need to drill a hole in the nut.

Then chip it out in pieces! After that is out, a prying tool will need to be utilized to pull the carrier out of the gear case.

Once that is out. You basically just punch the seals out into the carrier and then install the new seals from the inside of the carrier. Here is a video we made that demonstrates this process with a resealing of the gear case:

Otherwise, we will be utilizing the same methods as described previously!

Yamaha

Yamaha gear cases are probably the easiest to service!

These gear cases can all be serviced in the same basic way. Yamaha has not had any major changes done to the design of its gear cases for many, many years.

They are a great gear case and the prop shaft seals can be changed by either pulling the bearing carrier. Or by utilizing the quick way as we have described earlier.

Here is a video showing the service procedure for these gear cases:

Johnson/Evinrude

Most Johnson Evinrude lower unit prop shaft seals are pulled out from the outside. This means that they will be easily pulled out by utilizing one of the two methods.

The thing about these seals though. Is that they have a thicker metal frame to them. So they are harder to bend with the screwdriver.

But the drywall or screw method works really well.

It is just really important that you predrill the holes in the seal.

Unlike some of the other cases where you can run the screw right into the seal and then pull it out. For these seals, it is really important to drill the hole and run the screw into the hole.

It will help to prevent you from slipping off the seal and scratching the prop shaft.

Suzuki & Honda

Both Suzuki & Honda have the ability to change the prop shaft seals without pulling the carrier.

The same warnings come with these lower unit seals as well. Be very careful if you are using the screw method!

The seal puller method will probably be better for these gear cases. If you are not that comfortable with the entire process, then it will be a lot safer than the screw method.

It’s also important to keep in mind that ALL manufacturers recommend that the bearing carrier be removed. In order to change out the prop shaft seals.

The two methods that we have talked about today. Are a way of getting the job done, but at a risk as well.

We recommend pulling the carrier if you are not that comfortable with doing it. Either of these two ways that we have shown you here today!

Check Us Out!

Now that you know how to change your prop shaft seals. Here are some other great articles that you will find extremely helpful!

Does YOUR Boat Have The Right Propeller? & How To Check!

How To Tie Up A Boat! Don’t Wake Up With it Underwater!

We’d also like to invite you to check us out on Our YouTube Channel! Where we do all kinds of How-To and DIY videos. To help you learn more and more about your boat and how it works!

Aaron Hilligoss

Aaron has been working in the Marine Industry for over a decade and holds certifications for Yamaha and Mercury Marine. It is not uncommon for him to own and be working on at least three different boats at any given point in time!

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