Section 3 - On The Water
90-864195070 JUNE 2007 Page 55
Propeller Selection
IMPORTANT: The engines covered in this manual are equipped with an RPM rev‑limiter
that is set to an upper (or limited) RPM amount. This limit is slightly above the normal
operating range of the engine and is designed to help prevent damage from excessive
engine RPM. Once the RPM returns to the recommended operating RPM range, normal
engine operation resumes.
It is the responsibility of the boat manufacturer and/or the selling dealer to equip the power
package with the correct propeller. Refer to Mercury Marine's web page http://
www.mercurymarine.com/everything_you_need_to_know_about_propellers6.
Select a propeller that will allow the engine power package to operate at or near the top
end of the recommended WOT operating RPM range with a normal load.
If full throttle operation is below the recommended range, the propeller must be changed
to prevent loss of performance and possible engine damage. On the other hand, operating
an engine above the recommended operating RPM range will cause higher than normal
wear and/or damage.
After initial propeller selection, the following common problems may require that the
propeller be changed to a lower pitch.
• Warmer weather and greater humidity cause a loss of RPM.
• Operating in a higher elevation causes a loss of RPM.
• Operating with a dirty boat bottom causes a loss of RPM.
• Operating with increased load (additional passengers, pulling skiers) causes a loss of
RPM.
For better acceleration, such as is needed for water skiing, use the next lower pitch
propeller. When not pulling skiers, do not operate at full throttle when using the lower pitch
propeller.
Getting Started
20‑Hour Break‑In Period
IMPORTANT: The first 20 hours of operation is the engine break‑in period. Correct break‑in
is essential to obtain minimum oil consumption and maximum engine performance. During
this break‑in period, the following rules must be observed:
• Do not operate below 1500 RPM for extended periods of time for the first 10 hours.
Shift into gear as soon as possible after starting and advance the throttle above 1500
rpm if conditions permit safe operation.
• Do not operate at one speed consistently for extended periods.
• Do not exceed 3/4 throttle during the first 10 hours. During the next 10 hours, occasional
operation at full throttle is permissible (5 minutes at a time maximum).
• Avoid full throttle acceleration from idle speed.
• Do not operate at full throttle until the engine reaches normal operating temperature.
• Frequently check engine oil level. Add oil as needed. It is normal for oil consumption
to be high during the break‑in period.
After Break‑In Period
To help extend the life of your Mercury MerCruiser power package, the following
recommendations should be considered;
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