Choosing the correct prop for your boat can mean the difference between a well performing motor,
and an engine that is low on power which is lugging or over revving. A lugging or over revving engine
will eventually fail to engine damage. The prop must be for the proper application, be it an outboard,
inboard, or I/O, a noticeable differences being the hub design, hub diameter, and spline.
The most important features of the prop is the diameter and pitch, as this will determine the rpm of the
engine. It is very important that the engine operates in the proper rpm range of the engine determined
by the manufacturer. For a proper rpm test an actual water test will need to be performed. The engine
will need to be run up to full throttle operation and trimmed for optimum performance. The tachometer
must be in proper operating condition for making the correct choice of prop. The motor must not be allowed
to over rev. Once the rpm is determined the correct prop choice can be made.
If the engine is over revving, a higher pitch prop is required, and if the engine is running at a
too low of a rpm a lower pitch prop is needed to bring up the rpm. The more pitch in a prop the more water
the prop will move in one revolution of the prop. A 2" change of pitch will in most cases change the rpm
by 300-400 rpm. Engines normally can use two different pitch propellers, say a 19p and a 21p and stay in
the operating rpm range. The lower pitch prop would be considered a power prop as it will run at a higher
rpm and have much more torque, which is good for heavy loads or sking. The higher pitch prop would be
considered the speed prop as you would loose your bottom end (torque) but gain on speed as you would be
pushing more water at the same rpm. A prop for example, 14 1/2 x 19 would have a total diameter of
14 1/2 inches and a 19 pitch.
Now the question, aluminum or stainless steel? There is pros and cons for both. The aluminum prop is a
good economy prop, as the price is within reason for the average boater. It will have some flex and can
be damaged easily. But on the other hand minor repairs are cheap, and if you hit something hard you are
more likely to damage the prop verses something in the gearcase. Now with a stainless prop which is much
more expensive there will be less flex and better performance, but with a stainless prop if you hit
something damage to the gearcase is more likely to occur.
The last thought that may come to mind is a 3 blade or 4 blade prop? A three blade prop does quite well
for normal use, but you may consider a 4 blade if you are having problems with blow outs, ventilation,
or cavitation. A four blade prop will give you a much better hole shot, less slippage, but the top end
will not normally improve and with a possibility of dropping a few rpm. Performance boats and bass boats
are good candidates for this prop.
The interchangeable hub assembly is available for props with a 4 1/4" and 4 3/4" hub diameter, thus
allowing to interchange props from one engine manufacturer to another. This includes most v4-v6 outboards
including Mercury, Johnson, Evinrude, Yamaha, and Honda; also including sterndrives such as the Cobra
drive the Volvo SX drive and the Mercruiser #1, Alpha, and Bravo drive. When a propeller needs to be
replaced only the propeller and not the hub assembly need to be replaced. This is around a 50.00
dollar savings from the older intergrated aluminum hub/prop assembly. The interchangeable Michigan Wheel
XHS hub assembly will interchange with the Mercury and Mercruiser
If you wish to find the correct prop for your boat, please refer to the cross reference
prop chart provided by Michigan Wheel.
To order a propeller or other accessories for your boat visit our online
Blue Water Marine 8690 S. Oceana Drive, Montague Mi. 49437