I have been reading 18th century colonial American newspapers (mostly British North America) and have come across the work "turks" quite often. Was this term synonymous with "Muslim," and if not what would the term mean outside of religion?

Like the others, I would like to see the exact context, but I'm guessing the term was being used politically.

Most people in the Anglosphere had a fairly unnuanced view of Islam and the Ottoman Empire. Particularly to Whig political thinkers, the Turkish court was a perfect symbol of both tyrannical rule and immoral, hedonistic excess (think harems full of girls in Princess Jasmine outfits). This fit a broader narrative, first established by the opposition Tories when George I assumed the throne, that rulers from the East were inherently, naturally despotic. Being that this line of thinking associated the West with liberty and constitutional rule, it became quite popular among American Whigs/Patriots/Revolutionaries.

For more on this, see Bernard Bailyn, The Ideological Origins of the American Revolution.

The other answer is true, but it probably misses the mark over what your confusion is about.

Before 1750, and particularly before 1700, the word "Turk" in British North America was occasionally used to refer to an "Indian", i.e. "Native American" or First Nations person.

The context is important because the word at the time did have several different meanings. In one meaning, it referred to the people actually from the area of Turkey. If you read accounts of Captain John Smith of Virginia's battles with the Turks, for example, those accounts are actually referring to his naval experience in Mediterranean waters off the Turkish coast.

"Turk" was also used as a catch-all term for all Muslims, as this 18th century book illustrates quite well. The "Turks and Indians" are Muslims and Hindus the author is trying to convert to Christianity.

"Turk" was also occasionally used in the sense of any non-converted person (non-converted to Christianity, that is). It's this sense that is probably confusing you. For example, Francois de Laval, bishop of the Catholic church in Quebec, wrote in 1663:

"Many missions new, or to be begun at once, as soon as the Turk of these Churches shall have been slain—I mean the Iroquois."

A year earlier, in 1662, the people of Brooklyn, New York, raised money for the "ransom [of local man] Tunis Craeyen's son Jacob, then a prisoner among the Turks." Craeyen wasn't a sailor and there weren't enough Muslims in New York at that time to be kidnapping anybody. Again, here they are referring to the local First Nations population, known at that time and in that area for kidnapping local farmers and holding them for ransom.

As one later historian put it, "The Indians were the Turks of America." In the earliest surviving documents, you might even see reference to "Turkish grain" which meant corn.

The sense of "Turk" referring to a First Nations person had mostly gone out of fashion by 1700, though you still see occasional uses of this meaning into the mid-1700s. By the time of the Revolutionary War, "Turks" almost always meant somebody from around the area of present-day Turkey or else, less frequently, a Muslim in general.

EDIT: Spelling