888 to 140 housing swap

Odiesoxx

Cadet
Joined
May 14, 2017
Messages
9
Couldn't fin an old thread on this, so here goes.
Just bought a 74 bonanza 18 foot with the 188 up mercruiser 888 drive. The upper housing is broken where the tilt/trim cyl attaches. I was given a second boat with a mercruiser 120/140 with a bad engine. I know the ratios are different, so can't just swap,the outdrive, but can I swap the upper housing? Are they the same? How tough is it to swap the gears out? I am mechanically adept, as a 25 year auto/aircraft mechanic, but haven't ever dug into an outdrive before. Any help is appreciated!
Darin
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,092
remove the drive, remove the engine , swap inner and outer housings.
If you can do a rear end, you can change the gears
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Swapping internals means running through the shimming procedure. The tools to do that alone will cost more than a new upper complete.
 

Odiesoxx

Cadet
Joined
May 14, 2017
Messages
9
Along these same lines, I have looked for a printable service manual link for this setup (188hp 888 drive), but the links I have found are dead or corrupt. Can anyone point me to a good link?
 

Odiesoxx

Cadet
Joined
May 14, 2017
Messages
9
okay, I found a link for a manual that works, but now I have another question: where is the gear reduction in the drive? Top ring and pinion, or bottom ring and pinon. if it is at the bottom, can't I just swap the complete upper half with gears and shafts installed?
 

Bondo

Moderator
Staff member
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Apr 17, 2002
Messages
70,464
Ayuh,.... Welcome Aboard,.... Gear ratio is determined in the upper unit,....

The lowers are all 1.65:1,....
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Welcome to "BOAT"ing.... Break Out Another Thousand.....
 

Odiesoxx

Cadet
Joined
May 14, 2017
Messages
9
Not new to this game, had an 85 30 ft party barge and an 84 50 ft Myacht on Powell. What is new to me is sterndrive. Always had outboards before.
 
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