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#572393 - 04/25/19 09:53 AM Bravo cone clutch slipping fix  
Joined: Jul 2003
Posts: 6,669
Dave R Offline
Dave R  Offline

Joined: Jul 2003
Posts: 6,669
Raymond NH
I got a private message recently about fixing slipping bravo cone clutches without the need to buy new parts. Thought I'd share my experience and success.

Most of the time, the forward clutch fails long before the reverse clutch fails because it gets much more use. The fortunate thing is that the forward and reverse gears and clutches are identical and can be easily swapped. The obvious symtom is slow engagement of forward gear. Sometime it will not engage until the throttle is opened a little and it will then bang into gear. Everyone's gut reaction is that the lower cable needs to be adjusted, but that is not likely going to fix it.

To fix on the cheap:

Get a Mercruiser Service Manual 11 for clarification and details of the following steps

Remove the drive
Drain at least a quart of oil out of the drive
Mark the driveshaft retaining ring relative to the upper gear case housing so that it can be tightened back to original torque without any special tools.
Remove the driveshaft retaining ring (you can tap it off with a hammer and a punch if you don't have the correct tool)
Remover the driveshaft assembly, it should slide out with a little stiction.
Remove the rear cover from the upper gear case housing. Don't lose the shift detent ball and spring
Remove the upper cover from the upper gear case housing. Shim and bearing race will likely stick to the cover, the outer bearing may or may not stick. Don't lose any of these bits.
Remove the shift shaft, shaft cam, and shift fork. A retaining bolt from the shift cam should thread into the top of the shift shaft and give you a good purchase to pull the shaft up and out.
Note the orientation of the upper and lower gears and the cone clutch. You will be flipping all three parts over upon re-installation so don't get them mixed up
Remove the upper gear, cone clutch and lower gear.
De-grease and clean the cone clutch mating surfaces on the "back" side of the gears.

The following step is one that I came up with and is not recommended by Mercruiser. It may seem weird, but it works and will get you more life from your clutches
Being very careful not to get any grit or metal into the bearings, use 80 to 150 grit sandpaper to gently roughen the cone clutch mating surfaces with vertical scratches. You just need a few light scratches all the way around and don't need to go nuts.

Please consult the manual for re-assembly

Clean the cone clutch and gears then lube and re-assemble into upper gear case with all three parts flipped over so that the former reverse gear is now the forward gear. Note the balancing marks.
Install the upper cover
Install the shift cam, shift fork and shift shaft.
Install the rear cover
install the driveshaft assembly and ring
ensure shift mechanism that accept the shift cable is pulled all the way out of the drive on the front side. This is really important.
install drive
refill oil
test that the drive shifts N F N R N F N . The drive should go into gear very positively come out of gear instantly.

water test

Last edited by Dave R; 04/25/19 09:54 AM.

"Mischief Managed II"
1992 Tollycraft 44 Cockpit Motor Yacht
Twin CAT 3208TA inboards
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#572407 - 04/27/19 11:16 AM Re: Bravo cone clutch slipping fix [Re: Dave R]  
Joined: Aug 2005
Posts: 2,476
WayWeGo Offline
WayWeGo  Offline

Joined: Aug 2005
Posts: 2,476
Oakton, VA
Great advice!

I did that on my Bravo 1 drive when I had it apart. It was not slipping but there was obvious wear. I figured I would extend the life of the drive somewhat by reversing the gears, though I did not do any sanding. It lasted at least until I sold the 23 year old boat.

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1975 Trojan F36 Convertible, Twin Chrysler 440's
2014 West Marine AL360 Inflatable, 1966 Mercury 6HP, 1992 Mercury 20HP

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