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Bravo Upper Gears - Shimming?

Old 04-06-2007, 07:28 PM
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Default Bravo Upper Gears - Shimming?

When replacing bravo upper gears do you have to re-shim?
I have a 2000 bravo III that I recently replaced the upper gears but have run into a problem. I replaced the two driven gears and the one pinion gear. I set the bearing pre-load on the pinion gear and now when I start to tighten the spanner nut the drive just tightens right up to the point I can hardly turn it. I have the original .094 & .091 shims in the correct location. I have read and re-read my manual and search to try and find an answer, all seem to be that bravo's do not require shimming. That would lead me to think my new gears have a problem? Any info is appreciated
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Old 04-06-2007, 09:47 PM
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You have to change the race on the upper tower and top cap to the smaller one. Once this is done it should load ok.
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Old 04-06-2007, 10:13 PM
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When I recently replaced my gears, I had to do some research into the shims. Merc changed dimensions on those shims. It is in the service bulletin on www.mercruiserparts.com if I remember correctly. It sounds like you may be driving the pinion too deep into the driven gears. The bulletin on gear replacement along with your part numbers will let you know if this is the problem that you are having. Also check the gear engagement pattern with some prussian blue. I had a hard time finding any info on backlash for the upper gears and just went with engagement pattern. I also have a vague memory of a similar problem when I put mine together and ..... Just remembered . Forget everything I said before for now. Pull the input shaft and make sure that the ring between the bearings spins easily. If it doesn't, you're going to have to tap the bearing on the input shaft end loose and reset your preload. I had to do it a few times to get it right, but mine worked out perfect. The stuff on the shims may still apply, you'll have to check part numbers to know, but I think that the ring is too tight between the bearings (bearing over press). The manual has instructions on doing this work

Rene

Last edited by oldandtired; 04-06-2007 at 10:20 PM.
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Old 04-06-2007, 11:16 PM
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Pettem,
When you say you replaced the upper gear set, are they the new style "thick floored gears" or just like the ones you removed? If the bearing inside the driven gears is 1" then they are the old style. If it is less than 1" (about 7/8") then they are the new style. If you installed new style, everything needs to be replaced in the upper. New gear kits offer all the pieces. The new style gears also require differnt shims. They are about .040" thinner.
In any case the upper gears should be lashed for proper operation. Also the preload on the pinion gear bearings, if set correctly, will not allow the ring between the two bearings to slip around. Set preload with the pinion gear and bearings in the case.
Give me a call tomorrow and I can help explain it better on the phone. 616-335-8446. If I am on the net, the answering machine will tell you so.. call me back in about 15 or so.. thanks

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Old 04-06-2007, 11:29 PM
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I had to go back to the service manual to remember exactly how my problem went. I had a tough time setting preload because of the over-press that was on the bearings, making the ring tight. Like I said, it was a vague memory. Back to the shims. The mercruiser parts site does have all of that info in the service bulletin when you go looking at the gearsets though. I would have called Mr Gadgets myself, but I don't like to bother people if I don't actually know them and we aren't doing business. I am glad that people like him are on this board to help the rest of us out.

Rene

Last edited by oldandtired; 04-06-2007 at 11:32 PM.
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Old 04-07-2007, 02:22 PM
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I figure that if it were me needing info there would be someone that I might be able to talk with.
I dont mind talking to fellow boaters that are having problems figuring something out that I have been thru. If I can help, why not! I would hate to have someone make things worse by not having the knowledge to do it correctly.
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Old 04-07-2007, 09:09 PM
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Thanks for all the responses...

I have been doing some more research myself and found the service bulletin pertaining to the gear change in 2000. I guess the only question I have yet to get a concrete answer on is do I need a new upper drive shaft? I know I need to use the .040 thinner shims and also need to install a bushing in the drive housing and cover plate but do I need to also replace the upper shaft and clutch?

Thanks again for the help
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Old 04-07-2007, 09:23 PM
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Serial # will determine if you have to shim or not, the newer bravos' do need to be shimmed. A few new tools but not difficult.
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Old 04-08-2007, 01:05 AM
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Pettem,
I take it you are trying to install new thick floored gears in a drive that did not have them previously? If so, the upper shaft doesnt need to be changed, but the cone clutch, shift fork, tower races, all need to be changed. That is if you are trying to install new X (thick floored gears) in an OL drive..
Hope this makes sense..
And all the bravo's need to be shimmed, just what thickness is the trick question. To do it properly, you need to measure the lash on each gear. The cases are different, the top caps are different, and the pinion depth will be different. A properly setup drive is essential for long life..
Just my .02 on the subject.

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Old 04-08-2007, 08:53 AM
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This sounds exactly like what I am trying to do. My drive is and OL and this is why the new gears didn't drop in.

So this is what I need to do?
1.) I already have the new gears - done
2.) Find and purchase a new clutch and shift fork assembly?
3.) Find and purchase the new shims and bushings that go into the OL drive
4.)Set the lash and go boating?

Thanks again for all the help

Note: Does anyone know a good place to buy the clutch and shims etc. I know about the kit but I already purchased the gears. Also, a good website indicating any of what we have been discussing? Thanks Again Mike
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