Diameter, Cupping, & Drag... All Keys to a Good Propeller

by Super User
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A term that is important to know when choosing or replacing your boat propeller is diameter.  To determine diameter of your prop measure first determine the circumference (which is the distance around your prop) and then measure from one side propto the other straight across to get diameter.  A majority of manufacturers determine the propeller diameter based on the pitch & horsepower of the boat but diameters are really limitless based on personal preference. A general rule of thumb is; the lower the pitch of a propeller is the larger the diameter will be.  

Cupping is another term that you will need to know when discussing your propeller.  Most propellers have some level of cupping to them, which is where the final trailing edge of the propeller has a bend or curve that tilts away from the boat.  Cupping helps to increase overall performance by increasing pitch which will also lower the rpms. The placement and severity of the cupping determines the rpm and overall performance of the propeller/boat.  

A final term to keep in mind when deciding on the appropriate propeller for your boat is drag.  Drag is the slowing down that occurs when the underside blade is in the water. If vibration and calibration could be controlled a propeller with one blade would be the fastest and most efficient due to a lack of drag (but we all know that it is not a feasible way to create propellers due to many reasons).  As blades are added to the propeller the drag is increased. But the argument for more blades is that it will decrease the time between load and unload time (of water) which will make the process seem smoother. Propellers can come with anywhere between 2 and 6 blades and the ideal number is based on a great deal of factors including pitch, engine capability, and use of boat.  

 

Fuel Usage: Is Your Prop To Blame?

by Super User
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Have you noticed an uptick in your recent fuel consumption?  Are you filling up more than you were last year? What many propefficiencypeople fail to realize is that boat props are important to efficiency.  When choosing a prop the primary concern should be to make sure it allows the engine to turn up to a speed within the specifications of the manufacturer (usually within 500 revolutions of rpm).  This helps to lengthen the life of your engine as well by not lugging it down or letting it over-rev. There are many other properties to a prop that have an effect on the efficiency for your particular boat including, number of blades, pitch, and skew.  We could help you determine which prop type would be best for your boat that would be most efficient.

In fact, a bent or dented prop can rob you of 10% of your fuel costs right off the top.  We can use our machinery to determine how far out of specs your prop is and can then either repair it or suggest a replacement.  Contact us today! 

 

Learning About Your Propeller

by Super User
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There is so much more that goes into a boat propeller than most people realize.  There are terms that we in the business use that are often times not understood.  Here is a good overview of a few of those terms to help you better comprehend the work that goes into perfecting your prop: Propeller Facts

What is propeller pitch?

Pitch is defined as the distance a propeller would move if it turned one time through a solid. Think of a screw going into wood. The distance it goes into the wood with one rotation is the pitch. When applied to boat propellers, the concept is a bit more complex since a 21" pitch propeller won't actually travel 21" through water due to variables such as drag, aerodynamics, ventilation, and cavitation. The difference between the theoretical pitch of a propeller and its actual progression in the water is called "slip." For the most part you shouldn't need to worry about either of these unless you suspect that your propellers pitch may be wrong for your boat and your boat motor. In this case, you can try to determine it yourself HERE or give us a call, and we'll help you find out if you have the right propeller pitch. 

What is propeller cavitation?

Propeller cavitation is the formation of air bubbles on the propeller due to pitting on the prop's surface. It usually occurs as a result of damage to the propeller and will be felt in the form of vibrations. Unless you are an expert in propeller repair and have the appropriate tools yourself, cavitation should be addressed promptly with a professional boat prop repair shop as it can damage the propeller itself as well as reducing efficiency and creating an uncomfortable ride.

What is propeller ventilation?

Propeller ventilation is when the prop sucks air, which is often caused by having the boat engine trimmed to high. It can also occur when boating at high speeds and jumping waves or in sharp turns, either of which can bring the propeller close to the surface of the water. Ventilation can cause the engine to over-rev and a signficant reduction in thrust. Unlike cavitation, ventilation issues can often be fixed by the boat owner fairly easily. If you have questions or concern, give us a call!

Do You Repair or Buy New When It Comes to Your Boat Prop?

by Indy Prop Shop Specialist
Hits: 62
Boat Prop

Many props can be repaired back to "like new" condition. On rare occasions when more than 1/3 of a blade is missing or severe metal fatique is obvious, we may recommend against it. However, we have a specialized machine shop and over 40 years of experience, so if it can be done, we can do it. We can provide prop reconditioning for aluminum props, stainless steel props, and nibral props. Bring your prop in or drop it in our 24/7 dropbox, and we'll take a look and let you know the best way to get back on the water fast.

Is a 3 Blade or 4 Blade Prop Better?

by Indy Prop Shop Specialist
Hits: 65
3 Blade or 4 Blade Prop

With modern designs, either 3-blade props or 4-blade props can be excellent all-around performers. Three-blade propellers are popular because they tend to provide a good blend of acceleration, fuel efficiency, life, and speed. Four-blade propellers can improve acceleration, fuel efficiency, or lift, but were often considered slower. However, improvements in design engineering of modern 4-blade props have really negated that issue.

Which type of propeller depends more on what is best for your specific boat and motor as well as the type(s) of boating you do and what performance factors are most important to you. For example, 4-blade props can provide increased water displacement capability, lift, and grip, which can enhance handling and fuel efficiency among other factors. Even with improved designs, though, the addition of the fourth prop does create additional drag and can reduce top speed. Call us or come by the shop at 1401 Maxine Rd. in Indianapolis, and we'll talk through your setup and help you identify the best prop for your boat."