Anyone know the Gear Ratio for a 1961 Evinrude 40HP Big Twin?

[newhamburgboating]

Title has it all folks!

Thanks in advance,

Steve

 

[racerone]

According to the brochure it would be 12 / 21

 

[newhamburgboating]

Awesome thanks! where did you find that? I spent some time this morning trying to find it.

 

[racerone]

Just old time knowhow !-----I can look in a factory sales brochure of which I have many.--Or look in the parts bin and count the # number of teeth.----Or look on parts websites and count the # of teeth.---Or put motor in gear and turn flywheel 10 revolutions and count how many times the prop rotates.

 

[newhamburgboating]

Well then, can you crack your book of secrets and let me know the WOT RPM range too please? haha. Just put a tach on, looking to do all the calculations and such to find the right prop for my setup.

I saw in one place 4500 -5000, but then here on iboats under prop shopping it shows 4500-5500. Raining today so cant check actual RPM until that clears.

 

[steelespike]

I'm conservative I would stick with 4500-5000 for a 61.
Unfortunately my old manuals only list the rpm at which the hp was developed. 4500.
4500 -5000 certainly is reasonable.

 

[newhamburgboating]

Thanks Steelespike, probably looking at the same manual i am