Clean the bilge is good advice
But don't just dump some bilge cleaner and/or bleach in it and call it done... Would you clean a dirty bathtub by throwing some tub and tile cleaner into the dirty bathwater and then leave it there? Would you skip the rinse cycle when you run the clothes washer? Of course not...but it's amazing how many people think that's the way to clean a bilge. Unless you thoroughly rinse it out, all you've done is emulsify the dirt and slime--and maybe killed off enough bacteria to knock odor down for a little while...but it's all still in there...ychhh!!A really good detergent bilge cleaner, such as B.C. (available from the online store right here), not only will emulsify any remaining diesel in your bilge, but it will also break loose and clean out all the critters, dirt, slime etc. Rinse very thoroughly...then leave all hatches open so that plenty of fresh air can circulate through the bilge to dry it out completely. Unless you have a leak, that should cure your problem.