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Old 15-04-2016, 14:45   #1
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Changing ring gear

I have a Rosborough Trawler with a Volvo Penta, TAMD40B

I need to slide the VP MS3 reverse gear our of the spline, to get to the flywheel.

Any guess on how far back I need to move it, to clear the spline and get it out of the way ?

Hoping to do it in the water. I can slide the shaft back some, just not sure how much right now.

If I knew how much room I need, I will break the coupler and measure the gap.

Engine room access is great, just don't want to haul and pull the rudder.

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Old 15-04-2016, 15:20   #2
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Re: Changing ring gear

You might want to take a look here:

I was going to say about 2" to get the shaft clear, and this says 50mm, so I'm guessing it is pretty close to that.

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Old 15-04-2016, 15:20   #3
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Re: Changing ring gear

The spline on the MS3 reverse gear input shaft engages the spline on the spring damper plate about 1" to 1.25 ".

If you can move the prop shaft aft that much then its an easy job. If you cant move the shaft that much, you can still get the gear off but it takes a little more muscle.

Here is the way to do it:
It might be helpful to remove the exhaust hose from the exhaust elbow to obtain better working room, depends on your installation.....
Close the thru hull valve and disconnect the water cooling hoses from the gear box. Remove the shift cable. Break loose and remove the four bolts holding the prop shaft coupling to the output flange of the gear and slide the shaft coupling aft at least enough to get the coupling pilot disengaged from the pilot recess on the gearbox flange.

Loosen and remove the six bolts holding the MS3 to the flywheel cover plate. Wiggle the gearbox housing a little to get it loosened from the pilot in the flywheel cover plate. Lift up on the gear housing a little so that its loose in the cover plate and rotate the entire housing 90 degrees to the left or right, which ever is easier. Because its a drop center gear, this will rotate the gearbox output flange up and away from the prop shaft flange and allow you to slide the gear box aft and disengage the spline from the spring plate. Then you can set the gearbox aside and remove the flywheel cover plate and expose the flywheel. Reverse the procedure on the way back together.

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Old 15-04-2016, 16:23   #4
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Re: Changing ring gear

Thanks guys, great info, especially rotating the box to the side.

I have a drive saver and a 1" spacer in the coupling now, plus I can just get the prop off, with the rudder on.

I should have plenty of room.
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Old 15-04-2016, 16:39   #5
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Re: Changing ring gear

Since I have your attention, can the ring gear be flipped or do I need a new one.

Thanks again.
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Old 15-04-2016, 18:49   #6
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Re: Changing ring gear

No ring gears I've seen can be flipped, I have rotated the gear on the flywheel. If the gear has some mangled teeth in the area the starter usually engages you can rotate it 90% or so where the starter engages on good teeth. A starter pinion usually engages the flywheel in the same place on most starts, I've also used a die grinder to dress up the teeth in the area that need it.

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