A lack of punctuation makes it a little difficult to workout exactly what you're after. Are you after a free outboard, advice on what outboard to get or advice on where to get an outboard?
Edit:
Also, how far along this project are you? Commercial insurance, commercial river licence & commercial safety certificate all sorted?
Not wishing to sound harsh but if someone was to donate an outboard, quite feasibility a good few thousand quids worth, I assume they'd want to know the project was taking shape and not just a whim....