Patent ID: 8277270
Filing Date: 2012-10-02
Classification: B63H

Abstract:
1. A boat propulsion unit comprising: a power source; a propeller arranged to be driven by the power source to generate a propulsive force; a shift position switching mechanism having an input shaft connected to the power source, an output shaft connected to the propeller, and a hydraulic clutch arranged to change a connection state between the input shaft and the output shaft, a shift position of the shift position switching mechanism being switched between forward, neutral, and reverse by engaging and disengaging the hydraulic clutch; a control device arranged to adjust and maintain an engagement force of the hydraulic clutch to be any value in a range of 0% to 100%, including any value between 0% and 100%, of the engagement force of the hydraulic clutch by adjusting a hydraulic pressure applied to the hydraulic clutch and thereby vary a rotational speed of the output shaft with respect to a rotational speed of the input shaft; and a retention switch connected to the control device; wherein when the retention switch is turned on by an operator, the control device controls the engagement force of the hydraulic clutch to assist a hull being retained at or propelled toward a predefined position; and the control device calculates the engagement force of the hydraulic clutch based on a boat speed integral value, which is a speed of the boat integrated over time since the retention switch was turned on.