Difference between drive shafts on yamaha 60-70-80-90hp 2stroke outboards

[MattiRonn]

Hello! Does anyone have clue which models that has which drive shaft dimensions? My Yamaha 90hp -88s lower unit has a 20mm 18 splines drive shaft, but i need a new one and i have been looking at different lower unit that are for sale, but i havent found anyone that fits! I have seen both 16 and 14 splines driveshaft!

[boscoe99]

Would it help if you knew all of the other lower units that used the same drive shaft as the one that is in your model motor? Or, the same or similar lower units that are used on other models?

[99yam40]

I am still trying to figure out what a Yamaha 90hp -88s is

[boscoe99]

I just guessed it is a 1988 model two stroke Yamaha.

Folks don't like to disclose too much about their motors over the innerweb. More secretive than a social security number it would seem.

I cannot think of a single reason why Yamaha would ever publish dimensional tolerances for their parts. Next thing you know someone would what to know the alloy of the steel. How it was heat treated. What type of machines were used in the manufacture of it.

[donsmarine]

Maybe Bay Manufacturing could help 419 499 4602

[MattiRonn]

Would it help if you knew all of the other lower units that used the same drive shaft as the one that is in your model motor? Or, the same or similar lower units that are used on other models?

Hello! yep, i meant that if any other lower units than the 90hp uses the same drive shaft!

[boscoe99]

This link indicates the models that used part number 6H1-45501-11-00 drive shaft.

https://www.boats.net/product/yamaha...d792e83eaef758

[MattiRonn]

Ok, thx for answer! I have a new question! Can i take the driveshaft from my 90hp lower unit, and mount it on a lower unit that have been on a 70hp? the part of the driveshaft thats above the waterpump are 2mm thinner on the 70hp than the 90hp, but are they same size down inside the gearhouse?