The Volvo Duo Prop in Action

Some marine propulsion systems use two propellers mounted at some distance from one another along the stern edge of a watercraft.  Other dual prop systems take a different approach entirely, placing two propellers onto a single engine.  This is the case with Volvo duo props.

First introduced in the early 1980s, Volvo duo propellers were a true leap ahead in marine propeller technology.  Volvo propellers using duo prop technology feature twinned propellers that rotate in opposition to one another in order to cancel out any lateral forces that may be acting on the watercraft.  This essentially means that all the forces left tend to drive the boat forward instead of allowing it to veer to one side or the other.

Advantages of Volvo Duo Propellers

Because lateral forces are no longer an issue, these duo props provide boating enthusiasts with a faster rate of acceleration even as they optimize fuel use for better efficiencies.  In addition to acceleration that may be more rapid by as much as a full third of the previous rate, Volvo duo props also increase the top speed that is possible for a watercraft.  In some cases, this improvement has measured as much as 5%.

Improvements in fuel consumption are equally impressive.  When only a partial load is in play, fuel efficiency may be reduced by as much as 10%.  At the same time, boaters will experience lowered levels of both noise and vibration, which helps to create a more pleasant atmosphere for everyone aboard.

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Warning Signs: When You Need a New Prop

Experienced boating enthusiasts know to check the physical condition of their boat, motor, and propeller on a regular basis – and they know how to recognize the warning signs that indicate it is time to look for a new propeller.  Boaters may need to buy new Yamaha outboard propellers to replace their existing ones when they see, for example, evidence of cracking across any of the blades in their current propeller solution.  Other warning signs include bent blades or blades whose surface edges show signs of wear.  These usually show up as tiny missing pieces along the edge.

It may also be time to look into Yamaha outboard propellers of you notice a new source of vibration in your boat.  Propellers that are damaged can cause such vibrations, as can propellers that have been improperly repaired.  Another warning sign is that the propeller cavitates a great deal while under a load, or if you notice it slipping excessively.  While some cavitation and / or slip is to be expected due to factors such as driver error or the motor design, a great deal of either should not be tolerated.  Quite often, a better aftermarket propeller match can solve the problem.

A poor match of propeller can cause other kinds of performance issues.  For example, if the motor on your boat runs without issues, yet you cannot get it to achieve the RPM claimed by the manufacturer, the propeller may be the issue.  In this case, running the wrong propeller will mean wasting precious fuel.

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Prop Guide

A propeller for your boat’s motor is one of the most important items you will purchase when refurbishing or upgrading your watercraft.  To the consternation of many novice boating enthusiasts, however, there is an incredible multiplicity of propellers on the market today.  How can you be sure that you are not only purchasing a propeller that will fit your motor, but also one that will help the motor perform to its optimum ability? Simple – use a prop guide, also known as a propeller selection tool.

A propeller guide will answer the basic question regarding what size prop you need to purchase, but will also guide you to choose the propeller that best suits the needs you are trying to address, whether those needs include an increased top speed or less cavitation and vibration during your motor’s operation.

Some boaters are reluctant to use a helpful online propeller selection guide because the web forms involved generally ask them for a great deal of information – everything from the size and loading capacity of the boat to the type of material the hull is made of and the kind of fuel the motor consumes.  Only by requesting information on this level of detail, however, can the tool function as desired, narrowing down the nearly limitless range of choices to just those few propellers that are really right for you.

A propeller represents a considerable investment of funds, so be sure to shop for your next one by using a prop guide that will get you the results you need and deserve.

 

 

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Stainless or Aluminum outboard propellers?

stainless or aluminum propellersWhen you are shopping for a replacement prop for your boat you need to do your homework.  With so many different styles and sizes, choosing the right propeller can be a daunting task.  If you know you want a boat propeller with the same diameter and the same style of blades you need to move on to choosing a material.  There has been a lot of debate on whether stainless steel or aluminum boat propellers are better.  To make the best investment, you should understand the pros and cons of each.  Review the benefits and challenges of each and then make your decision.

Benefits of Aluminum Boat Propellers

Aluminum propellers are the most common because they are very affordable and offer good performance under most circumstances.  One reason why many boaters choose aluminum propellers over stainless steel applications is because aluminum weighs about half as much.  These propellers are also very easy to repair when damaged.

The Disadvantages

While aluminum is a great choice it can flex under extremely high rpms and this will cause a drop in pitch.  The blades often tend to be thicker than stainless steel blades so they will cause more drag.  They are not ideal for sandy conditions so you must consider use.

The Benefits of Stainless Steel Propellers

Stainless steel propellers are designed for high performance and they are the most durable choice on the market today.  They have thinner blades which will reduce dragging and will not flex when you are traveling at high speeds.  They are also designed for abrasive environments and can handle adventures in sandy and shallow waters.

The Disadvantages

One of the biggest setbacks has to do with price.  Stainless steel is simply a more expensive material and it is more difficult to repair when damaged.  These propellers weight twice as much as aluminum which means you need a more powerful engine.

Ultimately, the decision depends on use.  If you are not looking for power, the aluminum prop may be the right choice.  If performance is your primary concern, stainless steel props will better meet your needs.  Consider durability, pricing, and overall use when buying your boat propellers.

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The Need for Zinc Anodes

Boat zincs are an important part of a marine craft propulsion system because they keep other metals from corroding and deteriorating in the water.  What is not thoroughly understood by some boaters, however, is the fact that zinc anodes cannot do this vital function unless they are left in their original state.

This means that boating enthusiasts need to keep the boat zinc free of paint.  A surface layer of paint will smother the zinc’s ability to sacrifice electrons so that the other metals nearby need not do so.  This sacrifice of electrons leads to eventual corrosion.  Therefore, boaters should keep their boat zincs in original condition, watching them closely so that they can be replaced when they have worn away and a new zinc anode becomes necessary.

Not just for propulsion

Boat zincs are useful for protecting other metals.  When it comes to boats, this means that their usefulness extends far beyond the propeller area.  To be sure, propellers are typically guarded against corrosion by the presence of a zinc collar around the shaft, but metal rudders are also at risk of corrosion.  The typical boat zinc in this situation is a disk that is bolted onto a metal portion of the propeller.  Lest the addition of boat zinc create turbulence or drag, zinc anodes for use on rudders usually have a shallow shape that is slightly domed.  This helps them to present a streamlined profile when attached to a rudder so that boat performance can remain high.

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The Need for Aftermarket Boat Props

Those who are new to the leisure activity of boating may not be aware of one key fact about outboard propeller engines. In most cases, the propeller that ships with an outboard engine is a “stock” part and is not, in fact, the ideal propeller for every boat that may elect to include that particular type and model of outboard motor.  Stock boat propellers such as these tend to be designed along “compromise” principles that will allow the motor to be used with a large number of different boats.

Depending on the hull and load that the motor must eventually contend with, however, these boat props may range in performance from average to unsatisfactory.  The solution to this problem is to look at the range and variety of aftermarket boat propellers instead.  Choosing the correct propeller for a specific boat and engine will allow the engine to run properly at its rated horsepower, which is usually marked clearly on the engine cover.

Outboard engines are supposed to be able to run at their maximum rated revolutions per minute – this situation creates peak efficiencies.  The wrong propeller can cause an engine to run at an exceptionally high RPM.  This leads to faster wear and tear on engine parts because it creates additional friction.  Too few revolutions per minute are also inadvisable since it causes carbon build-up as well as poor fuel utilization.  The right boat propeller, however, can help boaters to avoid both of these situations so that they can derive maximum use and pleasure out of their watercraft.

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Understanding Propeller Function

Boating enthusiasts who make regular use of their outboard engine and propeller do not always understand how a propeller actually works.  They may have in mind the action of a fan because fans, unlike propellers, are often seen while in operation.  A propeller working underwater is a more complex operation.

A propeller represents the very last stage in the power train or propulsion system of a watercraft.  In essence, the job of the propeller is to change torque, created by an outboard engine, and change it into usable thrust that will propel the boat forward.  Chrysler outboard propellers, like all propellers, are specifically engineered so that they will be able to control the revolutions per minute produced by the engine.  When the throttle is wide open, Chrysler outboard props should be able to hold the revolutions per minute to the range the motor’s manufacturer has specified.

If a propeller can do this, it is one sign that the propeller is a good match for that engine.  This is because if a propeller allows a motor to exceed the recommended revolutions per minute, the result is excessive wear and tear on the drive train as well as poor performance.  To get the most out of Chrysler outboard propellers there needs to be a good match between propeller and engine.  Otherwise, the engine will not perform at peak efficiency today and neither will it pass the test of time by lasting for the long run.

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Eliminating Cavitation

Boaters who know a great deal about propellers understand the importance of choosing one that will exhibit as little cavitation as possible.  Nissan outboard propellers, like all marine propellers, are not completely immune to cavitation issues.  However, when Nissan outboard props are correctly paired with an appropriate choice of motor, cavitation can certainly be minimized.  But what exactly is cavitation?

Cavitation: The Basics

Cavitation is a natural consequence of the action of a propeller underwater; the phenomenon has long been understood in a physics context.  Cavitation happens when small cavities in water are formed and then are instantly filled in with liquid.  It results from rapid alterations to the pressure being exerted on a section of water.  Cavities form because pressure is lower for a fraction of a second and they fill in as pressure increases.

Why Excessive Cavitation Should be Avoided

Too much cavitation can cause wear and tear on moving parts of an engine.  One common kind of this wear and tear manifests itself as metal fatigue on the surface areas of a propeller.  Just as a strong wire can be made to break by bending it back and forth too many times, so can surface areas become damaged as cavitation stresses them.

Marine propellers are tested in a wide variety of contexts during design in order to enhance characteristics that will help to reduce cavitation.  Still, the best way to reduce it still further is to make sure that your aftermarket Nissan outboard propellers solution produces a good match with your motor.

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Changing Your Boat Prop

Boating enthusiasts know that for all the wonderful times and adventures they have on their water craft, there is also a maintenance aspect that must be considered.  One periodic task that must be taken care of is changing out an old propeller for a new one.  This is not a frequent job; it needs to be done only when the existing propeller shows serious signs of wear or when it has been subject to an accident or some kind of malfunction.  Of course, some boaters also change their propellers simply to get better performance from their water craft.

Boat Propeller Pullers: A Handy Tool

The most useful tools a boater could have in this situation include boat propeller pullers.  With such a tool, the task of removing the old propeller becomes much simpler.

How to Use a Boat Prop Puller

Using boat prop pullers is not difficult, but for the job to go well, it requires a little advance planning.  First, take a pencil and use it to mark where the old propeller lies in the propulsion system.  You will use this mark later to make sure that the new propeller is seated in exactly the same location.

After that it is time to get the old propeller ready to remove. The first step is to turn the propeller slowly while you hold on to a ratchet around the retaining nut.  Do not loosen the nut 100 per cent of the way.  When the propeller is loose, it is time to use the prop puller, which is used to remove the existing propeller from the shaft it normally sits on.

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Outboard Propellers 101

Once you have the outboard motor for your boat it is important that you choose the right outboard propeller as well.  The propeller should be suitable for the type of boating that you plan to do, different props are available for shallow draft boating, for water skiing, trolling and for other types of boating.  You also need to make certain that the prop will allow the engine to reach the manufacturers recommended RPM’s when at full throttle or you risk damaging your propeller and engine.  Choosing the right propellers is critical for the performance of your boat and for your boating enjoyment.

Boat propellers are often described by their diameter and pitch.  The larger your engine is in horsepower, the larger diameter prop you will generally want.  The pitch describes how far the propeller advances with each revolution.  A lower pitch gives better pulling power, however if you use a propeller with a pitch that is too low you won’t be using all the power of your engine.  A higher pitch allows the boat to go faster, but this is only true if you have enough horsepower to keep the RPM’s at the optimum range.  A pitch that is too large makes the propeller heavy and it demands more power than the engine can provide.

After determining the proper diameter and pitch you need to consider how many blades to have on your prop.  Outboard propellers typically come with either 3 or 4 blades.  Unless you are running a high horsepower motor or using the boat for bass fishing, you will most likely want to choose a 3 blade propeller.  4 blade propellers are designed more for high speed usage with less steering torque and vibration at high speeds.  Water skiers can also benefit from using a 4 blade propeller.

The next thing to consider is the construction material of the propeller.  Outboard propellers can be made from aluminum, stainless steel, or composites.  Aluminum is the most common choice for the manufacturer’s stock factory equipment.  They are inexpensive and easy to repair and they work well in a wide range of applications.  Stainless steel propellers are more expensive, but they are also more durable and less likely to suffer damage.  Composite propellers are typically only utilized on very small horsepower applications, and are not nearly as popular as aluminum and stainless propellers.

Your main goal when choosing a propeller is to ensure that it allows the engine to perform optimally at wide open throttle.  Boat dealers and Prop Shops can provide you with formulas to determine the proper pitch, diameter and number of blades based on your engines power or horsepower.

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