VOLVO PENTA 21936288 Boat Trim System Trimming Raft Marine Propulsion D4 D6 D8VOLVO PENTA 21936288 Boat Trim System Trimming Raft Marine Propulsion D4 D6 D8 Boat engine trim at a touch Now, you can adjust the boat engine trim with the touch of a button. Four push buttons allow you to adjust bow down and bow up, list starboard, and list port. For a comprehensive overview, the boat trim indicators display the position of the port and starboard interceptor units.