This is one of the “private wild reserves” protected by MARENA and managed by the landowners; La Máquina remains almost completely unvisited by tourists. The views from the waterfall are gorgeous and the area is great for hiking and camping. There is a cheap food stand and a shallow bathing area; short hiking trails lead through the forest.
La Máquina is located halfway (15 minutes) between Diriamba [1] and the ocean, around Km 58. Buses pass the entrance all day long in both directions. The reserve is open daylight hours, entrance is $1.50, and it’s closed Mondays.
Links:
[1] http://www.moon.com/destinations/nicaragua/masaya/the-pueblos-blancos-and-carazo/carazo