On my 208, I don't shut the valves for probably a poor reason. My 208 will not sink per se. Yes it can fill with water and ruin everything in the bilge but at least I can find it at the slip and pump it out.
MyOtherBoat on the other hand will sink like a brick if the bilge and deck fill with water. That's the hull I am more concerned about. That boat also has plastic raw water strainers on several of the sea cocks and they can crack over time
MyOtherBoat on the other hand will sink like a brick if the bilge and deck fill with water. That's the hull I am more concerned about. That boat also has plastic raw water strainers on several of the sea cocks and they can crack over time