A good number of Devon records are available on Find My Past (subscription site).
In my experience, it's difficult when an ancestor marries before 1837 (when Civil Registration was introduced) as there is no father's name on the marriage entry. Plus marrying out of the area in which they were born usually means that no family or friends were witnesses to the marriage.
If he went to sea aged 11, then presumably his parent or guardian would have had to sign the papers (I have a similar situation with one of mine, but later). The National Archives website holds records of naval service (as do Find My Past), but there might be quite a few hits with what is, unfortunately, not an uncommon name.
This is the link to the research guides (you need to search for the navy ones as there are a few):
I am not an expert in searching for naval records, so perhaps others on this board might have better suggestions.