I have a 1999 Glastron 249 with SX outdrive and small Chevy V8. Where can water leak into the bilge when the boat is just sitting in the water (not running). There are no hull or transom cracks. Boat took on about 1.5 inches of water being towed about a mile to get in on the trailer. Owner said "a" bellows would need to be replaced. A bad exhaust bellows wouldn't cause this?