Need help/advise - washed down the boat at the carwash on Sunday, it's a 18' Striper Walkaround. On the way home, checked to make sure the water was draining out, bilge pump working, pumped water out all the way home. Got home and put the cover on like normal, all good. Next day, walking past the boat, I could hear the bilge pump on. Scrambled inside and checked (little difficult to do given location of pump - in "hold" behind the batteries, down by the drain - enough room in the hatch for me to get one arm in, a little light, cannot visually see it). No water, no obvious debris, no obstructions that I could feel with fingertips. Felt around till I could feel the "lift trigger" and pushed down, pump shut off. Came home last night, the pump is going. Checked again, same thing, no water/debris. Checked a couple of times last night and it hadn't come back on but this morning as I go out to go to work, it's whirling for all it's worth. Again no water, no obvious debris in the space. So I disconnected it's lead to the battery. What do you think is wrong and what should I do to figure this out ... this is the biggest boat I have owned and first experience having a bilge pump. Thank you in advance for your ideas.