See a sleep specialist to make sure whether or not he has sleep apnea
. If he has sleep apnea
, then treating it will take care of the snoring. Untreated sleep apnea can lead to hypertension, diabetes, obesity, depression, heart disease, heart attack, or stroke. As Curtis 1960 recommends, dental devices are available over the counter (or over the internet - two products that come to mind are puresleep and somnoguard). Dentists can make better fitting and adjustable models that work better.