Half a dozen mouse traps baited with bits of peanutbutter coated napkins...Check every week or so and reload...They will get the picture pretty soon, or you will kill all the travelling mice that hop aboard your boat..
I store my boat in a locked building and the rodents still climb aboard,so then they DIE!!!!
My daughter says I'm heartless,,,she's right when it comes to those filthy creatures
The stick flypaper type traps work well too .but get pricey if you use a bunch....
It is cheaper than the cleanup and potential damage though..