How can I find out the gear ratio of my lower unit? '86 70hp Evinrude

[Larry3215]

Im just starting the process of trying to fine tune the prop for my 1986, 70 hp Evinrude E70ELCDC.

I think it has the large gear case, its 4 1/6" diameter, but it has a 13 spline prop shaft.

How can I figure out what my gear ratio is to use in the prop calc programs?

Thanks in advance!

Larry

 

[emdsapmgr]

Re: How can I find out the gear ratio of my lower unit? '86 70hp Evinrude

The 3 cyl engines had two gearcase gearsets that year. The 75 gearset was 15:28 (.536). All other consumer models used 12:29 (.414)

 

[Faztbullet]

Re: How can I find out the gear ratio of my lower unit? '86 70hp Evinrude

The 20" 60,65,65C,70 and 75 have the same gear ratio(12:29) only the 15" motor is different as its the small gear case.

 

[Larry3215]

Re: How can I find out the gear ratio of my lower unit? '86 70hp Evinrude

Thanks guys!

Where do you find this info? Ive tried looking up the gear sets at several on-line places, but never could find out the tooth counts to figure it out.

 

[emdsapmgr]

Re: How can I find out the gear ratio of my lower unit? '86 70hp Evinrude

They are listed in the 1986 Evinrude sales brochure. Probably in the factory service manual also.

 

[Larry3215]

Re: How can I find out the gear ratio of my lower unit? '86 70hp Evinrude

Thanks!