How to variable speed ?

I just bought a 17' Xpress and it has a 71lb five speed trolling motor. It is way to fast on low speed. I think I saw a post one time on how to make a variable speed box for one. Any ideas ? If I could somehow cut all the speeds in half and have a switch for maybe a high and low range.

Hardhead,I talked to a local MG,MK shop before and he told me it would cost alway's as much to do that as it would to buy a new one.

Talk to Cane Pole. He has a circuit that will do it. Or you can watch on eBay for a Minn Kota Maximizer.

Thanks, I thought Cane Pole had a drawing or something on here one time that showed how to do it.