I have to say this depends on what you're towing. For my 16' C-dory, 10% of 1,800 lbs is fine (180 lbs).
For my 28' Bertram on its triple-axle trailer (17,500 lbs), 1,750 lbs is not OK. The CG of the trailer loaded is just slightly in front of the middle axle, resulting in a tongue weight of...