Steering Pull Adjustment; Impeller Clearance Adjustment; Worn (Dull) Impeller - Mercury 40 Service Manual

Steering Pull Adjustment

The steering on some boats will have the tendency
to pull towards starboard. This pulling condition can
be corrected by using a pliers and bending the ends
of the exhaust fins 1/16 in. (1.5mm) toward the star-
board side of the outboard.
a - Exhaust Fins
Impeller Clearance
Adjustment
1. The impeller should be adjusted so there is
approximately 0.03 in. (0.8mm) clearance be-
tween the impeller edge and liner. Operating the
jet drive in waters that contain sand and gravel
can cause wear to the impeller blades, and the
clearance will start to exceed 0.03 in. (0.8mm).
As the blades wear, shims located in the stack
outside of the impeller can be transferred behind
the impeller. This will move the impeller further
down into the tapered liner to reduce the clear-
ance.
2. Check the impeller clearance by sliding a feeler
gauge through the intake grate and measure the
clearance between the impeller edge and liner. If
adjustment is required, refer to "Impeller Remov-
al and Installation".
a - Shims
90-852572R1 JANUARY 1998

Worn (Dull) Impeller

leading
edge
a
Sharpen to a 1/32 in. (.8mm) radius by
removing material from bottom side only
The intake of gravel through the pump can round off
and wear the leading edges on the impeller. Some
conditions you may experience from a worn impeller
are (1) a noticeable performance loss, especially on
acceleration, (2) difficulty getting the boat on plane,
or (3) an increase in engine RPM at wide open
throttle. Check the impeller blades occasionally for
damage. Use a flat file to resharpen the leading
edges as shown.
Do Not sharpen or alter the
top side lifting angle
Enlarged
LOWER UNIT - 6D-15
View