hi Rudy: Definitely, a significant problem, at any time but in the confined space of a boat, more so. I recently read on the internet the availability of an electronic gadget that deters rats, mice and insects. It sends out an electronic signal to prevent their appearance rather than killing them. Might be worthwhile to check it out. I remember the cost which is anywhere from $50 plus depending on the make. Leonard Stern, INDIFFERENCE