2006-2010 Suzuki DF150 / DF175 4-Stroke Outboards Service Manual, Page 89Get this manual
ENGINE CONTROL SYSTEM
HIGH SPEED RANGE When the engine speed is above the preset value (), the ECM generates signal to turn the VSV OFF, and vacuum is no longer applied to the depression chamberWithout vacuum the shut off valve return spring returns and holds the valve in its normal open positionIn this operating mode, intake air is supplied to the engine through the high speed intake tract onlyThis enlarges the intake tract volume, improves intake inertia and efficiency, which increases the engines output power