Motorboat engine hand–arm vibration attenuation using dual-dynamic vibration absorbers under different engine gear vibration excitation

Direct contact with a small motorboat engine handle exposes operators to high vibration levels, risking hand-arm vibration syndrome (HAVS). This study investigates handle vibration transmissibility and applies dual-dynamic vibration absorbers (DVAs) to reduce vibration within targeted frequencies. A laboratory-scale rig simulates engine operation under varying speeds and gear conditions. Without DVAs, high vibrations occur at 45-50 Hz (Speed 1) and 95-100 Hz (Speed 2). The handle's natural frequencies (70-78 and 92-96 Hz) shift closer to target ranges with DVAs applied. Vibration is reduced by 42.08% in neutral gear (Speed 1) and 53.56% in forward gear (Speed 2). Transmissibility within 0-100 Hz shows a significant drop (<i>T</i>_s < 1), indicating reduced vibration from engine to hand. Standard No. ISO 5349-1-based weighting confirms that DVAs substantially lower vibration risks, helping to prevent HAVS in motorboat operators.