Adding a keyed switch to a pull start

[40horsebugbuster]

I'm picking up a boat tomorrow that has a late 80's 40hp yamaha tiller handle pull start motor on it. I am interested in finding out what is involved in adding a keyed switch as a form of anti-theft to the motor? I know the model number and other information is important, so I will be able to post back tomorrow that info if this is can be done.

[40horsebugbuster]

Update, 89 tiller handle 40hp sf. I would like to look into adding a rectifier as well, can I get some info on this as well?

[40horsebugbuster]

Any help? Please?