new case with no shims

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,306
buy special tools, use the factory manual
 

Bt Doctur

Supreme Mariner
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Aug 29, 2004
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19,093
Scott gives you the new procedure the old school is to assemble with machinists dye, spin, examine the marks, adjust heel and toe
 

harringtondav

Commander
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May 26, 2018
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2,438
I'd go with Scott. The upper hsg. gear shim tools give you cone point match and correct backlash. I suppose you could blue the gears up and get a good match pattern, then figure out how to adjust the shims for the correct backlash, whatever that is, and however you'd measure it.

But the backlash is important. Those gear teeth bend under load and need that clearance to avoid unwanted contact and interference. The lower prop shaft hsg uses a shim tool for cone point, and an involved process to check the .017"-.028" backlash.

That top gear set runs at WOT speed of 4600-4800 rpm. There isn't much room for error.
 

Bt Doctur

Supreme Mariner
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Aug 29, 2004
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If you know how to build rear diffs you can rebuild the drive.
 

wrench 3

Commander
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Aug 12, 2012
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2,108
I did my own quite a few years back with dye and the backlash specs from an OMC Cobra and it's still running fine. I've resealed it since and the gear wear looked fine.
However I wouldn't rebuild someone else's without the tools.
 
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