1998 Johnson Evinrude "EC" 9.9 thru 30 HP 2-Cylinder Outboards Service Manual, Page 262Get this manual
Jet Drive Adjustments Impeller Clearance Adjustment If loss of performance combined with higher than normal wide-open-throttle RPM is noted (or the RPM limiter actuates), check for wear between the impeller's edge and the water intake casing liner
INote Accelerated
impeller wear can occur when operating in waterways which have bottoms composed largely of sand, silt, and gravel
rn 1.place feeler gauge between the impeller and and measure To check clearance intake casing liner, through the intake grille
the clearance between impeller's edge Impeller Clearance
0.020 in(0,5 mm) Minimum to 0.030 in (0,8 mm) Maximum
PCE0084
2If clearance is more than 0.030 in transfer appropriate number of shims from below to above the impellerThis will move the impeller down and decrease clearance Moving one shim will reduce clearance approximately 0.004 in(0,1 mm)