1999 Volvo Penta "WT" Models Workshop Manual, Page 162Get this manual
Installation
1If installing new rubber bushings, apply 3M Scotch Grip Adhesive 1300 or OIK:: Scotch Grip Rubber Adhesive 1300 to outside of tips, and insert into inside of exhaust pipe2Position valve with longest lip pointing down, and insert into pipePush pivot pin through bushings and valve until pin end is flush with outside of pipeCheck exhaust valve for freedom of movement
I Note If valve is not positioned properly (long lip down), it will restrict exhaust flow and fail to prevent water backing up into engineBoat performance would be adversely affected, and engine may suffer water damage3Install intermediate pipe following procedure under Exhaust Hose and Pipe Replacement