Seeing the insurance side of things ( I am a agent that writes a number of boats ) --
Many sinking at lake powell are do to the air intake vents cut into the hull on the side of houseboats. If you take a look at the side of your hull toward the back of the boat, many have the engine space air intake cut into it. Usually this vent hole is located about 12" above the water line. Generally, you have this "hole" on both sides of the hull. --- when you beach a houseboat the back of the boat sits a little lower in the water --- this puts these vent holes even closer to the water -- large storm comes up, directly from behind, and water starts pouring in these vent holes -- the size of these vent holes far outweighs the small output of the bilge pump -- as water starts to fill the engine compartment, it gets heavier, and the vent holes get closer to the water -- next thing you know ---- boat sinks
What we are seeing is that some insurance companies are requiring these vent holes to be plugged, and new vents installed much higher above water line ( we did out boat, and put them in the steps leading up to upper deck ) this puts the vent holes on our boat about 2 1/2 feet above water line --