Might be the same issue I have. The keel gasket is bad. When no one is on the boat it takes on very little water. Put some weight in the boat and it takes on more water. Check to see if the bulge comes on when you are under power or move all the weight/people to the back. Also you might notice a drip coming from the keel when it is on the trailer. Make sure there is water in the bilge, don’t pull the plug, put it on the trailer and go back in 30 minutes to see if it is dripping. I just keep a spare bilge on the boat.