MerCruiser Bravo One Sterndrive Prop Shaft Replacement

Our MerCruiser Bravo One engine needed an output (prop)shaft replacement, but there’s a catch: MerCruiser has changed the assembly on the prop shaft for this unit. 

A few parts have changed, and our sterndrive motor is an older unit, so several adjustments had to be made when transitioning from the old setup to the new one. Watch the video above or follow the steps below to replace the prop shaft on a MerCruiser Bravo One sterndrive.

MerCruiser Bravo One sterndrive

See the parts diagrams: MerCruiser Bravo One Sterndrive parts

The old design is made up of a thrust washer, shims and the housing that goes into the O-ring against it. On the newer units, however, you have a load (retaining) ring, thrust washer, the O-ring and the housing that goes into it.

MerCruiser Bravo One sterndrive prop shaft replacement tools

The output shafts are the same, but the bearing carrier housings are slightly different. You’ll also need to pull the bearing off the old output shaft because there’s a washer down low that needs to get transferred over to the new prop shaft (more on that later). 

Tools and Parts - MerCruiser Bravo One Output Shaft Replacement

  • Ratchet and extensions
  • Flat blade screwdriver
  • Lower range torque wrench
  • Soft blow hammer
  • Punch tool
  • Retaining ring (or nut) removal tool
  • Slide hammer

Buy MerCruiser bearing carrier

Buy MerCruiser prop shaft

Some special tools are needed to get this job done, including a bearing carrier extraction tool and retaining ring (or nut) removal tool, both from Marine Tech and chosen for their ease of use. 

MerCruiser Bravo One sterndrive output shaft replacement tools

You’ll need a lower-range torque wrench that can take 15-25 inch-pound readings because you're measuring the rotation resistance as you tighten down on the load ring, so you’ll need that to get it set accurately.

MerCruiser Bravo One output shaft replacement tools

How to Remove and Replace MerCruiser Bravo One Prop Shaft

Step 1. Bring up the outdrive so the lower unit oil will drain out properly, then remove the vent screw up top with a flat-head screwdriver. 

MerCruiser Bravo One output shaft change

NOTE: When you remove the both the vent screw and the drain plug (next step), there may be a gasket or an O-ring that gets stuck inside the housing, so make sure you dig it out if it doesn’t come out with the screw.

MerCruiser Bravo One output shaft change gearcase lube

Step 2. Remove the drain plug at the bottom and let the lower unit oil (gearcase lube) drain out.

MerCruiser Bravo One output shaft change gear lube

NOTE: If the oil looks milky as it’s draining out, your motor has a water intrusion problem. Ours was changed not long ago, so it appears normal.

MerCruiser Bravo One prop shaft change gear lube

Step 3. Find the tab on the large washer that’s been bent in to hold the ring in place, then use a soft-blow hammer and a punch to unbend it and release the ring. 

MerCruiser Bravo One sterndrive prop shaft change

NOTE: Bend the tab back far enough where it's no longer in the channels, but also far enough for the retaining ring removal tool’s teeth to fully engage the ring, because if your boat is a saltwater boat, it might be heavily corroded and the tool needs a big a bite to remove the ring.

MerCruiser Bravo One sterndrive output shaft change

Step 4. Use the retaining ring remover tool to engage the teeth, then turn it counterclockwise to remove the ring and the washer behind it. 

MerCruiser Bravo One sterndrive output shaft replacement

NOTE: Make sure you don't damage the housing as you’re rotating the tool.

MerCruiser Bravo One sterndrive prop shaft replacement

MerCruiser Bravo One prop shaft replacement

Step 5. Insert the bearing carrier extractor tool, rotate it so the teeth grab on the back side of the housing, then remove the bearing carrier itself.

MerCruiser Bravo One output shaft replacement

MerCruiser Bravo One propeller shaft replacement

MerCruiser Bravo One propeller shaft change

Step 6. Remove the O-ring behind the bearing carrier, followed by the prop (output) shaft.

MerCruiser Bravo propeller shaft change

MerCruiser Bravo prop shaft change

Step 7. Use a slide hammer to remove the thrust ring and the shims.

MerCruiser Bravo output shaft change

MerCruiser Bravo output shaft replacement

NOTE: The shims that were in place are from the old system and will not be needed for the upgrade. Also, the difference between the old setup and the new setup is a different bearing carrier housing and different rings. However, the output shafts are the same, but we need to remove the lower bearing off the old output shaft to transfer it to the new one. The main difference between the two bearing carriers is the old one is a bit longer. 

MerCruiser Bravo propeller shaft replacement

MerCruiser Bravo prop shaft replacement

Step 8. Position the old output shaft on a press tool with a bearing removal tool, then press out the bearing to remove its washer so it can be transferred over to the new shaft. 

MerCruiser sterndrive engine prop shaft replacement

NOTE: Don’t reuse the bearing from the old output shaft, since you’re putting a lot of stress on the outside of the bearing and it could mushroom out as you press it.

MerCruiser sterndrive engine propeller shaft replacement

MerCruiser sterndrive engine output shaft replacement

Step 9. Press the washer into the new bearing onto the new output shaft

MerCruiser sterndrive motor output shaft replacement

Step 10. Install the load ring, thrust washer and O-ring that go behind the bearing carrier, then prepare the new bearing carrier by applying a light layer of marine-grade anti-seize lubricant around the outer surfaces.

MerCruiser sterndrive motor propeller shaft replacement

NOTE: Use only a marine grade anti-seize, which has aluminum in it. Non-marine grade anti-seize may have bronze or some other type of metal mixed in with it that'll cause galvanic corrosion.

MerCruiser sterndrive motor prop shaft replacement

MerCruiser sterndrive prop shaft replacement

Step 11. Pack the inside of the bearing carrier with marine grease.

MerCruiser sterndrive propeller shaft replacement

Step 12. Add a little marine grease to the prop shaft, and pour a little bit of lower unit oil onto the bearing. 

MerCruiser sterndrive output shaft replacement

Step 13. Install the prop shaft, followed by the bearing carrier, making sure the V shape at the top of the carrier is pointing up. 

MerCruiser sterndrive output shaft change

MerCruiser sterndrive propeller shaft change

MerCruiser sterndrive prop shaft change

MerCruiser sterndrive motor prop shaft change

Step 14. Install the locking washer, with the protruding tab going up into the housing. 

MerCruiser sterndrive motor propeller shaft change

MerCruiser sterndrive motor output shaft change

How to replace MerCruiser Bravo One sterndrive motor output shaft

Step 15. Apply some marine grade anti-seize lube to the retaining ring, then install it with the lettering and arrow facing out, and rotate and seat it with your fingers.

How to replace MerCruiser Bravo One sterndrive motor prop shaft

How to replace MerCruiser Bravo One sterndrive motor propeller shaft

Step 16. Use the retaining ring tool to lightly seat the ring. You'll know you're getting close to 8-12 inch-pounds when the prop shaft doesn't have quite so much play, and you’ll feel some resistance as you're starting to compress the ring. Rotate the tool clockwise in quarters turns to prevent overtightening. 

How to replace MerCruiser Bravo One sterndrive engine propeller shaft

NOTE: We found there wasn’t enough play on our prop shaft, so we had to take our new setup apart and use a thread cleaning tool, because there was corrosion in there and it wasn’t engaging properly. We needed to carefully clean out those last couple of turns to bring it in and set the rolling resistance. Skip the following readjustment steps section if your installation tightened correctly. 

Readjustment Steps (17-21)

Step 17. Place a towel into the prop shaft housing, then add cutting oil to each of the teeth and on the threads of a thread cleaning/chaser tool.

How to replace MerCruiser Bravo One sterndrive engine prop shaft

Step 18. Start turning the thread chaser tool by hand just to make sure it goes smooth, then insert a 27mm socket to the handle of the tool and turn it. If the tool starts to bind up a little bit, reverse it just for about 1/8th of a turn and then keep going. Check the threads to make sure they’re clean.

How to replace MerCruiser Bravo One sterndrive engine outputshaft

How to change MerCruiser Bravo One sterndrive engine output shaft

How to change MerCruiser Bravo One sterndrive engine propeller shaft

Step 19. Reinstall the load ring, thrust washer and O-ring seals.

How to change MerCruiser Bravo One sterndrive propeller shaft

Step 20. Reinstall the new output shaft, bearing carrier and retaining ring. 

How to change MerCruiser Bravo One sterndrive prop shaft

Step 21. Use the retaining ring tool to tighten the ring down in small increments to avoid overtightening it. 

How to change MerCruiser Bravo One sterndrive output shaft

NOTE: Aim for a rotational torque of somewhere between 8-12 inch-pounds, which will be measured with a torque wrench (next step) as you continue turning.

Step 22. Use a torque wrench to get a measurement of 8-12 inch-pounds. If the measurement is under 8 inch-pounds, continue doing quarter turns with the retaining ring tool and the torque wrench until you achieve the correct amount of torque.   

How to change MerCruiser Bravo One output shaft

NOTE: Remember not to overtighten this, otherwise you’ll have start all over again with another load ring. 

How to change MerCruiser Bravo One prop shaft

How to change MerCruiser Bravo One propeller shaft

Step 23. Use a slide hammer if you need to straighten the retainer ring all the way up, then bend in the washer tab over the ring to lock it in.  

How to replace MerCruiser Bravo One propeller shaft

How to replace MerCruiser Bravo One prop shaft

Step 24. Install a new anode and you’re done.

How to replace MerCruiser Bravo One output shaft

How to replace MerCruiser Bravo prop shaft

 
ANODE
Mercury

ANODE

Qty.
THRUST HUB
Mercury

THRUST HUB

Qty.

 

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