The new Manzanillo bus station is located just inland from the Las Brisas beach area just north of downtown. See image below.
Manzanillo Bus Station photo from Sparks
Lobby area photo from Sparks
Interior of the modern bus station photo from Sparks
Manzanillo Bus Station, looking much like an airport photo from Sparks
Playa Las Brisas at left, downtown at right, bus station circled