Less than Optimal Performance
To determine the engine’s listed power rating, all Volvo
Penta engines are tested and certified at the following
conditions:
Condition Value
Air temperature 25°C (77°F)
Barometric pressure 100 kPa (14.5 PSI)
Relative humidity 30%
Fuel 87 AKI (90 RON)
When troubleshooting a suspected reduction of power
or speed consider the test conditions above. If actual
conditions are significantly different than any of these
variables, a reduction in speed is expected. High
ambient temperatures, high humidity, low pressure or
low octane fuel can all reduce power and speed.
In extreme cases these conditions can cause
detonation or spark knock. The engine’s computer
constantly monitors for this condition. If detonation is
detected, the computer reduces spark advance to
reduce the detonation and the engine damage it can
cause. Reducing the spark advance reduces power.
Performance of the boat as a complete package is also
based on similar test conditions. Variances in boat
performance can usually be traced to differences
between actual conditions and the test conditions.
The condition of the hull also influences performance.
See Hull Weight and Boat Bottom that follow.
Hull Weight
Total boat weight is an important factor in performance.
This is a combination of the boat and the passengers
and gear that are on the boat. Any increase in boat
weight will reduce boat speed. To minimize this
problem, do not store un-needed gear on your boat.
Overloading with passengers also causes problems.
If adding a significant amount of weight to the boat,
such as generators, appliances, coolers and other
heavy items, consider the effect of the added weight
on performance.
Fiberglass boat hulls can absorb a significant amount
of water over time, becoming progressively heavier. As
the boat becomes heavier, the original propeller (and
in some cases the drive ratio) may no longer be correct
for the boat. Hull weight was a major factor in the
original selection of these components.
If boat performance has declined over time and added
weight is suspected, consult an authorized Volvo
Penta dealer to discuss the issue. Your dealer can
assist you with selecting the correct propeller size or
gear ratio for your boat.
P0020436
Troubleshooting
47712779 09-2020 © AB VOLVO PENTA 67
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