Hi Bigford,
It probably would spin a bit fast, but there is always gearing

It depends on the size of the boat and what you want to winch. At the moment I am playing with a small motor as I am on letting out some rope with a little fish float on the end. What I do with that is drive around the boat the I want to tow back so that the rope catches onto it. Then I drag the boat back with my tow boat. The gearing doesn't need to be super strong as when I apply the motor, it is only winching in the rope and the float.
However if you wanted to winch a boat in, then a bigger motor is definitely needed, and some serious gearing is a must. I have found a bunch of educational kits from [link=http://www.tamiyausa.com/product/item.php?product-id=70167]Tamiya[/link] that are small and provide you with a set of gearing to slow down motors. If you wanted to retrofit your Sears drill into the gearing I couldn't see a reason that it wouldn't work. Most motors will spin fast when you turn the on, but the gearing you apply will slow it down, and give you more torque.
Hope that helps,
Greywolf20k