Tuesday, July 10, 2012

Bravo II Outdrive upper case repair and Dis-assembly?

MerCruiser Bravo 2 Outdrive will not get forward.

The Previous issue:---
Boat not going forward.
The shift cable was inspected faulty and replaced.Still the same issue,due to this Gear case was inspected to check the linkage.
Noticed ground up bronze/metallic pieces in the housing.



  • Issue 1: You need to disassemble the clutch/drive gear assembly to confirm the internal damage.
  • Issue 2: Dis-assembly procedure for Upper Gear case to repair Upper gear case.

BOTH these will be covered below with proper details and instructions.

This problems are not at all rare.Common issues and seen many times.

First of all confirm and check few things:

  • When the problem occurred Was the oil up over the gears in the upper case?
If it was it could be an issue with "re-entry damage" or just a failure.


This problems are sudden problems.What actually occurs with re-entry damage is,that the boat will be cruising along with no issues, and the boat is driven over a large wave and the prop actually comes out of the water.
NOW when the prop comes out of the water the prop is unloaded and the cone clutch floats out of the gear cups due to the rpm rise from the unloading.

NOW when the drive re-enters the water, the cone clutch slams into the gear cup and damages the pieces or welds the cone to the cup.

This is the problem which you notice if you have oil over the gears in the upper case.
BUT,suppose if you have not had a re-entry issue.

And still  the oil is up over the gears in the drive when the failure occurred, then you have a very rare part failure.
In this case the upper case itself needs to be disassembled.

Inspect both lower case and the oil quality.If oil is dirty,then it also needs to be changed.

Inspect the upper case gear housing.If the housing is damaged,then its major case.The housing with gear case needs to be replaced.

You cannot damage the gears and or the cone by any action in taking them apart. The parts in the upper housing are junk at this point. The one worry you could have is, not damaging the housing, it is still usable should you decide to rebuild the upper drive.
If the housing is fine,then you can rebuild the upper drive.

So first inspect and check what is exactly damaged inside it.
Depending on the overall condition of the drive we would probably replace the effected parts in the upper and not replace the entire upper drive unit.
But to perform that also you need to disassemble the lower and clean inspect and reseal it as part of the process. The drive oil is shared and you need to be sure it is clean in the lower drive.


If you have the manual then all procedure is mentioned in it.
If you are planning to buy the manual,then please dont buy aftermarket universal manual.It is not showing exact procedure for your unit.It shows common procedure which is not similar for your boat.

Its recommended to buy Mercruiser Manual.Its available from dealer or online from there website.

In upper case disassembly and rebuilt you dont need any special tool.All regular common tools will do the disassembly and repair for you.

But if  gear bearing races needs to be replaced,then special bearing removal tool is required.If you dont have the tool.You can get it on rent from Parts store.

The Procedure begins here:

Follow the step by step instructions:----

1- First remove the input shaft.The shaft is held by the nut.Exactly  behind the u-joints is a spanner nut holding the input shaft into the upper gear housing.
If your regular wrench socket is not helping to loosen the nut,then dont force the nut threads will get damaged and removing it will become very difficult.Thin in that case  you need a special tool. (There is a special tool for the spanner nut, can be purchased after market from any boat yard or boat parts house)
2- If the Nut is not coming out right then,Warm the housing just behind the spanner nut.
You can use a propane torch and don't get irritated with the heat, or start a fire. It will slide out.In some cases it comes out right,but some times it takes time to get the spanner nut loose.
3-Once the Nut is out.Then remove the top cap and the rear cover. Look for a ball and spring on the rear cap, not to loose it.

4- The shift fork will have to be removed before the gear will rise through the top cap opening.

To do this remove the Allen head cap screw from just under the fork/cam assy.Its easily  visible from the rear cover hole. Also without forget remove the Allen head cap screw holding the shift arm assy on the same shaft as the fork assembly.
When the two bolts for shift arm assembly and fork assembly are removed the shaft will easily slide out the top of the case.

To complete this step  take a 1/4-28 fine threaded bolt and thread it into the top of the fork rod from the top, and pull it out through the top with a pair of pliers.

5- Once this is done you can remove the fork assembly and the shift arm assembly through the rear cover hole.

6-The gear set assembly is visible.Lift the gear set out from the top cap.
7-Push the gears together and remove the two 1/2 rings and the gear assembly will come apart.

8) Before removing any part,please note down the exact position of parts.If you have original owners manual,then it will help.But if you don't have manual,then re-assembly will be much difficult.

9) Keep markers and webcam ready.If you notice any part is very tricky to be removed,then click its picture and save and mark the parts position with markers.
This sounds funny,but it really helps,when you get stuck up with re-installing the parts.

As per personal experience.The dis-assembly is easy,but reassembly is more difficult in this boat systems.
To reassemble is a bit more tricky, lots of very important steps.Dont ignore any step and dont forget or miss any part. These drives are some kind of tough if put together correctly. If not, they will grenade before you can turn the key off. Follow the book and don't take any shortcuts or advise from local techs that don't know and you can do this. At our repair yard we mechanics have rebuilt some of these units though out the years, with no failures. A great drive system.But we have noticed,many new techs try there hand in rebuilding this drive systems and getting stuck up in between,without knowing which way to go further and then come at out yard or go to other professionals in this drive systems.

This details will help.
Hope all goes well.

Users Who Viewed This Problem Also Viewed:

Crank Seals Blown on Waveraider

How to remove Flywheel on Jet ski?

Jetski Sputters and Low RPM?

Jet Ski Not Starting?

Sudden Electrical Problem On Boat