SuperSeal Duct Butter is a good thing to carry on board your sailboat.

http://news.thomasnet.com/fullstory/15526/1

Buy a couple cans and, at the time of purchase, also buy about 20 feet
of plastic tubing that will fit the nozzle on the can.

When some obnoxious clown anchors right on top of you and runs his motor
or generator all night keeping you awake with noise and fumes just break
it out a can and cut off about five feet of the tubing and attach it to
the nozzle. Then the first time the obnoxious boat crew dinghies ashore,
put on your fins and mask and discretely slip over the side. Snorkel
over to the exhaust thru-hull and slide the tubing three or four feet up
into the exhaust pipe. Then squirt a good dollop in but not enough so it
starts coming out where it can be seen. Withdraw and discard the tubing
and return to your boat.

Then sit and laugh when the assholes come back and try to start that
noisy, smelly motor or generator. Bwahahahahahhahahahhahahaha! They'll
play hell trying to figure out why they motor won't run. You can wave
goodbye when SeaTow hauls their sorry asses off.

Wilbur Hubbard