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Old 29-05-2024, 19:31   #1

Join Date: Feb 2010
Location: Australia
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Gearbox removal hint

Has anyone here gone to great and painful lengths to push a propshaft far enough back to allow enough room for the front spline to clear the drive plate and flywheel housing???
You don’t actually need to move the propshaft aft more than 3mm I discovered this shortcut in what alcoholics call “ a moment of clarity” a few years ago with a really difficult coupling and stern gland and used it quite often where the lateral space allowed. All you have to do is remove all the bolts from the flywheel housing and rotate the whole assembly 180° ( drain the oil first) most gearboxees have an offset and as you rotate the assembly, the output flange rises above the shaft coupling and gives you the amount of clearance required to clear the drive plate. Hurth and mechanical ZF’s do it well and some of the larger hydraulic reversing gears but the heavier gearboxes need overhead support. All the shaft movement required is the height of the pilot spigot, usually 3mm.
I just did this with a Yanmar 3GM but had to remove the rear engine brackets to rotate the adapter plate and gearbox. A bit of lateral clearance to the engine beds is required but so far that’s never been a problem. This trick only works with” large offset”output shafts so not with a borg warner.
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Old 29-05-2024, 19:57   #2
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Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
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Re: Gearbox removal hint

Now why haven't I thought of that?

Good one, Pete!

Jim and Ann s/v Insatiable II, lying Port Cygnet Tasmania once again.
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Old 02-06-2024, 04:55   #3
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Re: Gearbox removal hint

“Moment of Clarity” ..... Good description! I had that same moment about 30 years ago when we were doing some gearbox ratio and propeller testing on a 38 foot twin engine Carver motor yacht. The gears were VP MS5 drop center/down angle gears. Six bolts and twist the gearbox 90 degrees and out it came...barely had to move the shaft at all...
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Old 04-06-2024, 05:56   #4
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Re: Gearbox removal hint

I will take all the clarity I can find. Thank you Skipperpete.
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gear, gearbox, removal

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