A tip, modified from something I read when I had to house-break a puppy years ago: Vinegar keeps the dogs from re-using this spot.

Unless you want to have the (literally) son of a b**** repeat this action, hose off the hull and then go over the affected areas with a sponge soaked in a mix of vinegar and water. It doesn't take much, maybe 3 or 4 ounces of vinegar to a quart of water.

The vinegar neutralizes the ammonia in the dog's urine and has a slightly offensive (to dogs) smell which will fade away in a few days. In the meantime the dog, or others in the neighborhood, won't be attracted to your boat.

I'm sure you don't want them confusing it for a fire hydrant or fence post.

PGJ