I have a Columbia 10.7 and have no leaks below the waterline. I doubt the bolt is leaking if it was tightened properly. I usually add a bit of life caulk to it before putting it in each spring. The increase of pressure while sailing or heeling is not sufficient to cause this bolt to create a leak that does not occur when simply sitting in the water. The bolt is at least 3 feet under water. So, the hydraulic pressure on the bolt is pretty significant. It would be leaking all the time.
It is possible if the leak happens while sailing and heeled over one of your through-hulls is allowing water to enter. First step is to check if it happens on one tack or both. If it’s a through-hull it will happen probably when heeled on one side but not both. Check to make sure all the through-hulls are tight. If they wiggle in any way, they could let water in when the boat is rocking and rolling, but it’s more likely that the leak is a factor of the heel and the location of the through-hull and outlet.