Hi. We have a Bennington Tri toon. We store this in a storage field across from the lake throughout the summer. We have found tons of walnuts in the big storage compartment in the back along with walnuts stored along the rails and nests. Last year they chewed through battery wiring. Can anyone advise how to keep these out before they cause more damage ? The boat sits 1-2 weeks between use and they gather each time it seems. Someone suggested an ultrasonic device - we do not have any kind of electricity there. Any advice appreciated !!!!!