Not that hard to change. However, some things to consider:

1. Do you plan on moving the motor back and forth between the two boats
often. This is a pain.
2. The Long shaft will work on the jon boat but will not be as efficient
and you stand a good chance of hitting something on the bottom w/ it if your
not careful since it does hang down a lot farther.

If you plan on leaving it on the boat as a kicker - yes go for it.
Definetly cheaper than buying another engine.
If you plan to still use the jon boat - I would buy another engine and save
the agravation.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

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"HankCoen" wrote in message
...
I have an Evinrude 9.9 4 stroke short shaft on an older aluminum jon boat.
I
want to convert it to a long shaft (Evinrude sells a kit for this) to use
it
on a new boat as a kicker, anyone know of any problems I could have doing
this. Should I just buy another motor. The new boat makes using a jack
plate
to solve the problem impossible. So changing the shaft would be my only
alternative. Any input would be helpful. Thanks