13
IMPELLER INFORMATION
The size impeller to choose for your jet drive depends upon the priority you place on speed, economy, efficiency, engine life
and noise. All of these factors are affected by impeller trim size. the six different impeller sizes offered for your American
Turbine, are listed across the top line in the Impeller Selection Chart. The largest impeller is the 9 1/2" and the smallest is the
C.
In general, the larger the impeller the more efficient it is. this means that for any given boat speed, a larger impeller will re-
quire less RPM from an engine than will a smaller impeller. The benefits of the lower RPM are better fuel economy, less en-
gine noise and longer engine life. In some cases these benefits may be achieved at the expense of a slight loss of top-end
speed (rarely more than 1-2 mph).
The maximum rating of the aluminum impeller is 400 BHP and 5000 RPM. To achieve maximum top speed Figure 1 must be
used. To utilize this table, it is necessary to know the RPM at which maximum horsepower occurs in your particular engine.
This information is obtainable from the engine manufacturer. Select shaft horsepower figure in the left column and move
straight across to the right until you see the recommended RPM of the engine. The impeller trim given at the top of this col-
umn is the choice for maximum top speed. Should the selection fall between two impeller sizes, the larger of the two is rec-
ommended. Top speed is variable with load and hull design. This chart is accurate only if the jet drive has adequate water
supply at maximum RPM.
Since the jet drive demands a constant load against the engine regardless of load, there is no danger of lugging the engine as
in an overloaded propeller-driven craft.
To Next Page
Loading...
Need help?
General
