First, make the boat
mozzie proof. You may find yourself making net snoods for the dorades, for instance, and net for the companionway
, as well. Then, any mozzies that come below can be dealt with with fast kill spray.
However, if your partner is allergic to the permethrins in the coils, he may also be allergic to the sprays. See if you can figure out what it is that is the active ingredient in the coils you are using (there are different compositions). If necessary, you both may have to take to wearing clothes that fully cover you, and which mozzies can't bite you. You may find that is pretty warm, but we don't want anyone being poisoned here. Are there any lotions, sprays, roll-ons, sticks, or wipes that keep him from being bitten?
Different species of mozzies carry different noxious diseases; some are dusk feeders, others, daytime, so arranging to not get bitten is pretty important--and not only just for comfort.
Good luck with it.