2006-2010 Suzuki DF150 / DF175 4-Stroke Outboards Service Manual, Page 58Get this manual
PERIODIC MAINTENANCE
ENGINE VACUUM CHECK
Engine vacuum is required for proper operation of the Multi-Stage Induction system used on the DF150DF175Engine vacuum is also an indicator of general engine condition1Warm up engine to normal operating temperatureMake sure engine idle speed is within specification2Stop engine and disconnect vacuum outlet hose from check valve3Connect special tools (vacuum gauge, hose and 3-way joint) between engine vacuum hose and check valve! 09915-67311: Vacuum Gauge 09918-08210: Hose joint 09355-35754-601: Hose 09367-04002: 3-way joint 4Start engine and run at idle speedVacuum reading on gauge should be within specificationVacuum specification (idle speed at 759.8 mmHg, sea level) 61 71 kPa (457 533 mmHg, 18 21 inHg) 5If vacuum is not within specification, further testing (leakdown test, compression test, etc and evaluation of engine condition is requiredPossible causes of incorrect engine vacuum Piston ring leakage Incorrect valve timing Poor valvevalve seatvalve guide condition Intake leakage Cylinder head gasket leakage Restricted exhaust