BLADES OF SPEED FOR BOATS   Leave a comment

Probably the most confusing aspect of boating is the choice of a right propeller.  There are multiple factors that go into the choice.  Such factors include the hole shot, top speed, fuel economy and the life of the prop. 

The higher the speed of operation the more likely it is the prop blades will leave the water momentarily during each revolution.  The resulting stress can cause cracks or even break off blades during expended use. 

One recent survey of boat owners found that most (well over half) run 2 to 4 props trying to find the best performance for their engines.  Less than 20 percent ran 1 prop and an additional 20 percent ran more than five. 

Experienced boaters find that getting the right prop for their boat is important.  Thanks to the availability of different hubs, materials and blade design boaters can experiment and find the right prop for their equipment.  It is best to strike a balance between price and performance. 

Thanks to the folks at Yamaha, here is a quick guide to prop terms.  

Most fishing boats, such as bass boats, come with a four blade steel prop.  Larger boats, such as pontoon boats, also have four blades for getting quickly up on plane and improving the grip to help maintain plane at slower speeds.  The later usually has larger blade areas to provide the thrust needed for turning control. 

When it comes to construction materials, props come in steel, stainless steel and aluminum.  Aluminum is usually the least expensive but is also less durable.  Steel props are a compromise between the aluminum and the polished stainless steel.  The later is best for salt water environment as they are more durable and reliable in such applications. 

Propeller size is referred to by a number.  For instance a 14 x 17 prop has a 14-inch diameter and a 17-inch pitch.  Pitch is the distance the prop travels in one revolution.  The shallow angle has a low pitch that produces greater pulling power and acceleration accompanied by lower top speed.  The sharp angle of a high pitch produces the opposite result.  As pitch increases so does the diameter of the blade.

Larger diameter props push more water and are often found on boats with heavy loads and motors that have more horsepower. 

The rake is the angle of the blade in relation to the centerline of the hub.  High rake means more speed and stability in rough water.  The downside is that it needs more horsepower to be most effective.  Without that horsepower performance suffers. 

Because most boat owners do not use their boats for the same purpose all the time one may want to have two or more props and change them to suit the use planned.  For instance someone wanting to fish may want a better acceleration from one honey hole to another.  A person taking the family for a cruise does not need that top end and is interested in fuel consumption.

A wise boat owner should discuss his planned use of the boat with the marina or marine mechanic before choosing a prop.

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Posted 04/08/2011 by Donald Gasaway in Boats, Freshwater Fishing

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