Irwin 28: Lil Walkabout: Converting to outboard?

My transmission needs to be rebuilt; the engine is the original gasoline Volvo from 1974.

I found a couple of pictures of Irwin 28 with the outboard motors.
This admittedly does not make the sailboat any prettier, but it helps with:

- no oil in the bilge,
- no fumes inside,
- no noise inside,
- lots of extra room for additional batteries, sails even future electric motor



I found these articles:
http://www.onlineoutboards.com/article_choosing_outboard_hp.html

http://www.stewartfam.net/arlyn/outboards.html

Seems like 9.9 hp  should be plenty with these features:
- 4 stroke
- 2 cylinder
- 12-volt charging

- high thrust prop 
- deep (long) prop 

Parts:

Outboard bracket from West Marine

Do you have experience with outboards on the Great Lakes? 

I would really appreciate constructive comments... 

UPDATE (August 13, 2008):

1) I have delivered the boat with a loaned 9.9HP 2 cycle up Chicago River, Chicago Harbor, to Belmont Harbor.

2) We sailed and motored in hefty winds with the same 9.9 HP, which was sufficient.

3) I hate to lean over the transom in heavy seas and cord-start the motor. I rather have the battery starter in the cockpit.