Tohatsu 4 Stroke MFS 2/2.5/3.5A Outboards Service Manual, Page 101Get this manual
Power Unit 35) Correction of Valve Seat
1Use valve seat cutter (commercially available item) to correct valve seatTurn 45 degree cutter clockwise to cut valve seat surface to make it smoothBe careful not to over-cut valve seatTurn valve seat cutter while pushing down evenly45