So you want to go to a non touristy lake, but one that has rowing boats for hire.
Hiring rowing boats is about the most touristy thing you can do.
The "busy" lakes are Windermere and Derwent Water. I believe you can hire rowing boats on Derwent Water.
I am not aware of any other lakes where you can hire rowing boats.
Ullswater and Coniston are fairly quiet lakes.
The very quietest lakes are *********, Ennerdale and Crummock, but they are all on the west side so more difficult to get to.
Bassenthwaite is also very quiet, and Hawswater is quiet but not really a lake, more a reservoir.
Even the busy lakes like Windermere and Derwent do have their quiet parts, The west coast of both lakes is rarely visited by people.
Map here:
http://www.croft-guesthouse.com/graphics/lake_ district_map.gif