Propeller Selection; Propeller Installation - Mercury 75 Service Manual

Propeller Selection

For in-depth information on marine propellers and
boat performance - written by marine engineers - see
your Authorized Dealer for the illustrated "What You
Should Know About Quicksilver Propellers... and
Boat Performance
90-86144).
For best all around performance from your outboard/
boat combination, select a propeller that allows the
engine to operate in the upper half of the recom-
mended full throttle RPM range with the boat normal-
ly loaded (refer to Specifications). This RPM range
allows for better acceleration while maintaining maxi-
mum boat speed.
If changing conditions cause the RPM to drop below
the recommended range (such as warmer, more hu-
mid weather, operation at higher elevations, in-
creased boat load or a dirty boat bottom/gear case)
a propeller change or cleaning may be required to
maintain performance and ensure the outboard's du-
rability.
Check full-throttle RPM using an accurate tachome-
ter with the engine trimmed out to a balanced-steer-
ing condition (steering effort equal in both directions)
without causing the propeller to "break loose".
Refer to "Quicksilver Accessory Guide" for a com-
plete list of available propellers.
1. Select a propeller that will allow the engine to op-
erate at or near the top of the recommended full
throttle RPM range (listed in "Specifications,"
preceding) with a normal load. Maximum engine
speed (RPM) for propeller selection exists when
boat speed is maximum and trim is minimum for
that speed. (High RPM, caused by an excessive
trim angle, should not be used in determining cor-
rect propeller.) Normally, there is a 150-350 RPM
change between propeller pitches.
2. If full throttle operation is below the recom-
mended range, the propeller MUST BE changed
to one with a lower pitch to prevent loss of per-
formance and possible engine damage.
1C-4 - IMPORTANT INFORMATION
Information" (Part No.
3. After initial propeller installation, the following
common conditions may require that the propel-
ler be changed to a lower pitch:
a. Warmer weather and great humidity will
cause an RPM loss.
b. Operating in a higher elevation causes an
RPM loss.
c. Operating with a damaged propeller or a dirty
boat bottom or gear housing will cause an
RPM loss.
d. Operation with an increased load (additional
passengers, equipment, pulling skiers, etc.).

Propeller Installation

WARNING
If the propeller shaft is rotated while the engine
is in gear, there is the possibility that the engine
will crank over and start. To prevent this type of
accidental engine starting and possible serious
injury caused from being struck by a rotating pro-
peller, always shift outboard to neutral position
and remove spark plug leads when you are serv-
icing the propeller.
1. Shift outboard to neutral (N) position.
2. Remove leads from spark plugs to prevent en-
gine from starting.
3. Coat the propeller shaft with Quicksilver Anti–
Corrosion Grease.
IMPORTANT: To prevent the propeller hub from
corroding and seizing to the propeller shaft, es-
pecially in salt water, always apply a coat of
Quicksilver Anti-Corrosion Grease to the entire
shaft at the recommended maintenance intervals
and also each time the propeller is removed.
4. Flo-Torque I Drive Hub Propellers – Install thrust
washer (a), propeller (b), continuity washer (c),
thrust hub (d), propeller nut retainer (e), and pro-
peller nut (f) onto the shaft.
e
d
f
c
90-830234R3 DECEMBER 1997
b a
NOVEMB