Propulsion system of boat

A propulsion system of a boat, the propulsion system comprising:

• at least one propulsion machine including a drive source, and a propulsor configured to generate thrust with dynamic power transmitted from the drive source, the at least one propulsion machine being provided on each of both sides in a left-right direction with respect to a center of a hull;
• a trim angle adjuster configured to adjust a trim angle of each of the propulsion machines on the both sides in the left-right direction with respect to the hull;
• and
• a controller configured to control the trim angle adjuster, wherein
• the controller is capable of conducting heel control of causing the trim angle adjuster to adjust the trim angle to a heel suppression angle set in accordance with an inclination in a roll direction of the hull to suppress the inclination in the roll direction of the hull, and
• while conducting the heel control, in a state in which the at least one propulsion machine has a trim angle further inclined rearward in a propulsion direction of the hull than a preset first trim angle reference value, and in a case where a preset first condition is satisfied, the controller causes the trim angle adjuster to adjust the trim angle of the propulsion machine so that the trim angle of the propulsion machine is the first trim angle reference value or so that the propulsion machine has the trim angle further inclined forward in the propulsion direction than the first trim angle reference value.