The field investigation did not locate the engine but a few historical sources provide some information. The piston had an 11 foot stroke and a diameter of 52 inches (Heyl 1967:171). The stroke length is verified by the crank which measures 5.5 feet between the centers of the crank pin and paddle shaft. Also missing are the hot well, air pump, condenser and valves. Marine beam engines had a fairly conventional arrangement (Figure 15)(Ward 1860:52-59). Unfortunately, the missing components could not be checked against a standard configuration and the engine mounts remained inaccessible during field work.
Pieces of the engine were found during a deep excavation in the center of the ship, 87 feet from the stem. The excavation discovered two cast iron cylinder fragments eight feet below the baseline. One fragment was removed for conservation and analysis. This fragment is part of the air pump cylinder and includes a flange and brass compression ring. The compression ring indicates the fragment is from either the top or bottom of the cylinder. The cylinder diameter was approximately 24 1/4 inches with a one inch wall thickness. Deep vertical striations mark the interior of the cylinder wall. These striations pass through an unidentified filler metal used to fill small voids and imperfections in the original iron casting. This indicates the striations occurred during use, apparently when particles in the water pumped from the condenser became trapped between the piston and cylinder wall.
The fate of the engine machinery is not known but some conclusions can be drawn from the air pump fragments. Early salvage to recover the engine for reuse would probably include removal of the air pump but the fragments seem to rule this out. If the Maple Leaf resembled contemporary ships in her engineering arrangements, the air pump sat very low in the ship just aft of the engine cylinder and was linked to the condenser (Figure 15). After the vessel sank, the air pump did not threaten river navigation as did the engine cylinder that protruded above the main deck. When channel clearing commenced in the 1880's, the engine was either removed from the wreck or destroyed in place. The small irregular air cylinder fragments suggest the latter, with explosives used to accomplish the work. Due to their close proximity, all engine components were probably destroyed at this time.
In 1870, the walking beam still rose above the water indicating the engine remained intact on board the Maple Leaf (Driggs 1870). Whether or not Ross destroyed the engine while clearing channel obstructions from the site in 1883 cannot be positively ascertained (U.S. Army Engineers 1882). The official report from the U.S. Engineers office in Jacksonville mentions "the contractor only had to remove the wheels, hog and gallows frame, and shaft" (Russell 1883). No mention is made of the engine.