Engine Gear ratio

[DUKE1]

Just wondering if you could tell me how or where to find the gear ratio for my motor. It's a 86 140 Johnson.

Thanks
Duke1

 

[ezeke]

Re: Engine Gear ratio

Try here:

http://www.kencook.net/Gears.html

Edit: I think that it is 13:26 and the TX models were 12:27
It will be in the specifications sheets in the beginning of the service manual.

 

[Dhadley]

Re: Engine Gear ratio

How many splines on the propshaft? That will tell us if it has a V4 case or if it has one of the V6 style cases.

 

[rickdb1boat]

Re: Engine Gear ratio

Looks like 2.00:1 with the 13 spline shaft...

 

[DUKE1]

Re: Engine Gear ratio

Thanks for the feed back. It's got 15 splines on the shaft..making it a V6 gear case I'm told.

Thanks,
Duke1

 

[ezeke]

Re: Engine Gear ratio

That would be the 12:27

 

[Dhadley]

Re: Engine Gear ratio

You could have 1 of 2 possible cases. The V6 style that came on some V4's was a 12/27 or 2.25:1 ratio. That's most likely what you have. A true V6 case is 14/26 or 1.86:1.

 

[ezeke]

Re: Engine Gear ratio

I agree with Dhadley in that the most likely is the 12:27 which is what I have.

The two gear cases look and are the same except for gears, however and could be switched. To be sure, turn the flywheel and count the prop revolutions.

 

[DUKE1]

Re: Engine Gear ratio

Thanks for the response...I'm going to show my lack of knowledge here...what am I looking for by counting the prop revolutions? What does 2.25.1 mean?

Thanks
Duke1

 

[Dhadley]

Re: Engine Gear ratio

On a 2.25:1 ratio it means the flywheel will turn 2 1/4 times to make the propshaft turn once.

Here's what we do to fo figure it out easily. If the lower unit is still on the motor, pull the plugs to make it easy. Mark the flywheel and propshaft. The marks don't have to line up with anything in particular, whatever's easy for you for counting.

Have someone watch the propshaft while you turn the flywheel. Look for the propshaft to turn 10 times. With a 2.25:1 ratio the flywheel will turn 22 1/2 (22.5) times. You could turn the flywheel just enough to make the propshaft turn one complete revolution. The flywheel should turn 2 and 1/4 times. We like the 10x deal just because it's more accurate. But in your case the flywheel will turn over more than twice (2.25 times) or not quite 2 (1.87 times) if it's a true V6 case.

If you use the 10x deal and it's a true V6 case the flywheel will rotate 18.6 times to turn the propshaft 10.

 

[DUKE1]

Re: Engine Gear ratio

Sounds good...thanks for the info..I'll try it.

Duke1