2009 Yamaha F40 Outboard Service Manual, Page 358Get this manual
General Periodic Maintenance 8Insert the dipstick and remove it againMake sure to completely insert the dipstick into the dipstick holeOtherwise, the oil level measurement may be incorrect9Recheck the oil level using the dipstick to make sure that the level falls between the upper level and the lower level bOil filter wrench a: (commercially available)
Wait for more than minutes after turning off the engine to replace the oil filter Make sure to clean up any oil spills3Install the oil filter, and then tighten it to the specified torque
10Start the engine and make sure that the oil pressure alert indicator remains offAlso, make sure that there is no oil leakageNOTICE: If the oil pressure alert indicator comes on or if there is oil leakage, stop the engine and find the causeContinued operation with problem could cause severe engine damage