Final answer:
The precaution to take while towing a trailered boat is to allow more time and distance for stopping due to the increased weight of the boat affecting the vehicle's braking dynamics.
Step-by-step explanation:
While towing a trailered boat, the correct precaution that should be taken is to allow more time and distance for stopping. When the boat is being towed, the weight increases significantly, changing the dynamics of braking compared to driving without a trailer. Therefore, it is important to anticipate stops sooner and apply the brakes gently but firmly over a greater distance to avoid any potential accidents. On the other hand, other options like staying close to the right curb while turning to the right, partially deflating the trailer's tires or keeping outboard motors down for stability are not generally advised, as they don't directly address the primary safety concern related to stopping distances when towing.