gear case ratio?

Johny25

Johny25

Petty Officer 1st Class
Joined
Feb 8, 2012
Messages
265
Ok I bought me a beautiful 93' Johnson 120 yesterday and I am getting mixed info on what the gear case gears are? Have done a lot of reading through here and other forums and have heard 2.25:1, 2:1 and even 1.86:1? I know there was large and small gear cases made for these V4's but from the measurements I took I have the smaller 4 and 1/8" diameter case. I know I can pull the plugs, mark the prop, spin flywheel and count revolutions of flywheel to prop etc......but I am sure one of you guys got the easy answer :) Model is J120TLETS
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emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: gear case ratio?

I'm reading from a 1993 factory sales brochure. The 140 engines all use a 12:27 ratio. The 120 engines all use a 13:26.
 
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steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: gear case ratio?

12:27 = 2.25:1 13:26 = 2.00:1 For those not acquainted with gear ratio calculation.
 
Johny25

Johny25

Petty Officer 1st Class
Joined
Feb 8, 2012
Messages
265
Re: gear case ratio?

emdsapmgr said:
I'm reading from a 1993 factory sales brochure. The 140 engines all use a 12:27 ratio. The 120 engines all use a 13:26.
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Thank you emdsapmgr, much appreciated. Got my 93' service manual ordered and on the way but wanted to know sooner ha ha ha. Heya steelespike im sure im going to see you again as im going to be re-propping this motor soon as I get the tach functioning properly. Gauges on the dash don't work (found out yesterday). I'm running a 17" pitch aluminum stock prop but think by the way the motor and boat performed I can turn a 19. But need to get my RPM and speed reading first.
 
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