2009 Yamaha F40 Outboard Service Manual, Page 181Get this manual
Power unit 3Start the engine and warm it up until the idle speed gets stable at 750850 rmin4Check the oil pressure
Power unit (check and adjustment)
Checking the compression pressure
1Start the engine and warm it up for minutes2Remove the clip from the engine shut-off switch3Remove all the spark plug caps from the spark plugs4Remove all the spark plugs, and then install the special service tool into spark plug holeNOTICE: Before removing the spark plugs, blow compressed air into the spark plug well to clear out any dirt or dust that may fall into the cylinder
Oil pressure gauge a: (commercially available) Oil pressure (reference data): at 60 (140 F) with SL 10W-30 engine oil and at 800 rmin: 230.0 kPa (2.30 kgfcm2, 33.4 psi) at 61 (142 F) with SL 10W-30 engine oil and at 3000 rmin: 480.0 kPa (4.80 kgfcm2, 69.6 psi)