I have a 20 year old West Wight Potter I'm restoring.

Can I use an outboard designed for a 15" transom such as
"http://shakyparts.com/briggs_stratton_outboard_motor.html" or do I
need a longer shaft?

Here in California, all outboards used on State or Water District
lakes must be CARB approved. This eliminates all carbed and all 2
stroke outboards. Most small outboards that are CARB approved are over
$1000. The B&S referenced above can be had new for about $600

Thanks in advance!