I’m specifically curious about seagoing canoes along the coast of the Yucatán Peninsula in the mid-1800’s. Were they still typically of the dugout variety, or had they evolved to canvas on a wood frame or some other construction? What size would they typically be? Were they fitted with outriggers?
It seems the dugout variety canoe mentioned in the question was likely to be the variety encountered still in the mid-19th century. An ethnology titled THE MAYA INDIANS OF SOUTHERN YUCATAN AND NORTHERN BRITISH HONDURAS by Thomas W. F. Gann, published in 1916 has a section concerning boat building:
The Indians living in the neighborhood of lakes and rivers possess dories or canoes which vary in size from tiny craft 5 to 6 feet long by 16 to 18 inches beam, capable of holding only a single individual, to large craft 25 feet or more in length, large enough to hold a dozen people. All their canoes are constructed by the simple process of hollowing out large logs, the more durable ones being made from cedar, the lighter ones from wild cotton (yaxche).
We can assume that if this was the process observed in 1916, it was likely also in use in the mid 1800s.
I have not found direct reference to 19th century use of dugouts at sea, but we do know they were used at sea at a much earlier time. A Wikipedia article on Mayan Maritime trade discusses an early sighting:
As of yet, there have been no discoveries of an intact ancient Maya canoe, however artistic representations from prehistory as well as descriptions from Christopher Columbus' son, Ferdinand, provide rich details about what these vessels were like. Ferdinand tells of an encounter with a Maya Canoe in the Bay of Honduras near the Bay Islands during Columbus' fourth voyage in 1506. Bartolomé de las Casas describes the encounter:
"There arrived a canoe full of Indians, as long as a galley and eight feet wide. It was loaded with merchandise from the west, almost certainly from the land of Yucatan, for that was near there [the Bay Islands], a matter of thirty leagues or a little more. There was in the middle of the canoe a shelter [toldo] of palm matting, which they call petates in New Spain. Inside and under this were their women and children, possessions, and merchandise, so that neither rain nor sea water could wet anything. . . There were in the canoe up to twenty-five men."
Since an earlier question by this OP indicate research into this time and location as a setting, it might be worth noting that during this time frame (mid 1800s) the indigenous Mayan peoples of the Yucatan peninsula were embroiled in a civil war of their own, the Caste War of Yucatán.
I'd like to offer another interpretation: the Mayans may not have been using oceangoing canoes at all by the 19th century. Smaller dugouts for inland waterways did continue to exist.
Larger vessels are more stable in the ocean, and the historical record of the contact period repeatedly mentions substantial Mayan coasting vessels; see J. Eric S. Thompson for the stories and details. However, Norman Hammond found no later evidence at all of large Mayan canoes. Specifically, according to Erik Vance,
... of the thousands of boats that once littered the coasts, all that has survived is a single canoe preserved in peat soil that dissolved almost as soon as it touched the air and a couple of paddles discovered in Belize.
Also note that the maritime port at Vista Alegre was abandoned 500 years ago.