Etec 115 hp shaft extention question

[gordonhg]

Etec 115 HP:
The dealer shipped a 20" instead of the 25" and won't pay for the double shipping to return the engine and ship the one that I ordered. So, I have to install an extention. The 20" model uses a V4 lower unit instead of the V6 lower unit so I would have to use a 13 spline prop.

I was expecting to use a Rebel 15 3/4 x 15 prop 15 spline prop on the 25" model. But will now have to add an extension and then use a smaller diameter prop. The 20" only supports a 14" prop and has a 2:1 lower unit instead of the 2.24:1.

Anyone using an extension on an Etec 115?
Will this be an issue?
Will performance differ?

Thanks!