Measure from the top of your transom to the bottom of your keel. If it is from 15? to 17? long you’ll need to get a Parsun outboards with a “short” shaft. If it is from 20? to 22? long you’ll need our “long” shaft outboard. Parsun outboards shafts are measured from the bottom of the engine mounting bracket to the cavitation plate on the lower unit. Generally most boats need either a short or long shaft although some boats require a 25? shaft (ultra-long shaft) outboard. We recommend that you consult with your local dealer to determine which is the correct shaft length for your particular boat. Now we supply two kinds transom height for outboards.
How to select the propeller for outboards?
Propellers have two basic dimensions; diameter & pitch. Diameter is the distance measured across the propeller hub line from the outer edge of the circle that is made by the propeller’s blades during rotation. Pitch is the distance that a boat will travel if rotated one revolution without any slippage. When describing a propeller both the diameter and pitch are given. The diameter is referenced first and the pitch is second. Therefore, a 11? x 9? propeller would have a 11-inch diameter and a 9-inch blade pitch.
Theoretically, a propeller with a 11-inch pitch, when rotated one full turn, would advance a boat 11 inches through the water. In reality, no 11-inch pitch blade will advance a boat 11 inches with one full turn. This variance is referred to as slippage. In general, changing to a higher pitch prop will increase your top-end speed but reduce your acceleration (reduce your “hole-shot” power). On the other hand, decreasing the pitch will increase your hole-shot but sacrifice some of your top-end speed. If the hole-shot speed is important to you, for example if you pull water skiers most of the time, then you would want to go with a lower pitch prop and sacrifice some of your top-end speed but increase your hole-shot speed to get the skiers up faster. UNDER NO CIRCUMSTANCES SHOULD YOU EVER USE A PROP WHICH WILL ALLOW YOUR OUTBOARD TO OPERATE ABOVE THE OUTBOARD’S RECOMMENDED MAXIMUM RPM’s! Remember that in any application, discrepancies in performance can result due to the different boat hull designs, the final carrying load and your particular needs. NOTE: It is highly recommended that the outboard be checked with a tachometer to ensure that the engine is operating within the correct MAXIMUM RPM RANGE.
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