A modular exhaust manifold includes a plurality of exhaust manifold segments coupled together along a common axis. Exhaust manifold segments include a water jacket tube defining a liquid coolant passage around each of the plurality of exhaust manifold segments. The internal combustion engine also includes a coupling assembly for joining adjacent exhaust manifold segments. The coupling assembly includes a plurality of annular sealing devices configured to fit within a first set of grooves formed on an end portion of a first exhaust manifold segment. The coupling assembly also includes a spacing collar configured to attach to the end portion of the first exhaust manifold segment and couple with a fixed radial flange formed on an adjacent end portion of a second exhaust manifold segment to join the first exhaust manifold segment and the second exhaust manifold segment.