A damper for an engine mounted with a motor includes a first rotating body directly connected with an end portion of a crankshaft, a rotor constituting the motor and being integrally mounted at the first rotating body, a second rotating body installed at an inner side of the first rotating body to be rotatable relative to the first rotating body, and a first damper spring, a second damper spring and a third damper spring installed to be elastically deformed along a circumference direction between the first rotating body and the second rotating body. The first damper spring, the second damper spring and the third damper spring are all disposed within the length along the axial direction of the motor.

A composite flywheel (13), comprising a primary flywheel (15) integral with an input shaft (31) and a secondary flywheel (17) coaxial with the primary flywheel (15). The secondary flywheel (17) and the primary flywheel (15) are constrained so that they can rotate freely with respect to each other. A coupling device (61) is further provided, adapted selectively to: transmit power from the input shaft (31) to the secondary flywheel (17); and disengage the secondary flywheel (17) from the input shaft (31).