Devices To Protect Engines From Damage After Prop Strikes Or Rope Fouling
For smaller engines, such as outboards, where the propeller is exposed to the risk of collision with heavy objects, the propeller often includes a device that is designed to fail when overloaded the device or the whole propeller is sacrificed so that the more expensive transmission and engine are not damaged.
Typically in smaller and older engines, a narrow shear pin through the drive shaft and propeller hub transmits the power of the engine at normal loads. The pin is designed to shear when the propeller is put under a load that could damage the engine. After the pin is sheared the engine is unable to provide propulsive power to the boat until a new shear pin is fitted.
In larger and more modern engines, a rubber bushing transmits the torque of the drive shaft to the propeller’s hub. Under a damaging load the friction of the bushing in the hub is overcome and the rotating propeller slips on the shaft, preventing overloading of the engine’s components. After such an event the rubber bushing may be damaged. If so, it may continue to transmit reduced power at low revolutions, but may provide no power, due to reduced friction, at high revolutions. Also, the rubber bushing may perish over time leading to its failure under loads below its designed failure load.
Weed hatches and rope cutters
New & Used Boat Propellers For Sale Design Considerations
When you are picking boat Propellers, it helps to know the designs that you could consider.
Usually, the diameter describes the blades overall size and this is usually measured starting from the tip. The boat propellers that have a larger diameter are capable of pushing more water compared to the smaller ones. This means that a boat propeller for sale with a wider diameter is superior to the smaller counterpart.
Usually, the diameter of the boat props for sale near me is determined by the product manufacturer. The pitch refers to the distance in which the propeller is able to move the boat when it rotates once. This does not account for any slip.
If a marine propeller has a lower pitch, it is capable of creating even more power because of the engine RPM. Regardless of this, the boat moves slower. Using a high pitch boat props makes it possible for the faster movement to be achieved. The boat travels a greater distance in this case. As you make your choice, it makes sense to pick boat propellers for sale that have a pitch that allows the RPM of the engine to remain within the operating range that it is meant to be in. When you go under the best range, the bolt lugs and you end up straining the engine.
Select The Right Boat Propellers For Maximum Performance
The drive train is an important system on any engine-driven vehicle, car, truck or boat. For land vehicles, the system concludes at the tires, where the rubber meets the road. There, the choice is simple: select the right tire for the roadway and intended vehicle use. The difference for water-based craft is, of course, that the drive train ends at the propeller which is the liaison of horsepower to the water. Selecting the right propeller is very important. Boat propellers are available in a wide assortment of sizes and shapes. Sizes are referred to in terms of diameter and pitch. To make the best selection, sync the propeller to the manufacturers wide open throttle range. The right propeller will turn the minimum engine RPMs required by the manufacturer with its throttle fully advanced.
The next consideration is diameter. This will also determine the propellers RPM capabilities. Overall engine performance can be improved by selecting the right boat prop. The number of blades is also a consideration. Standard rule is the fewer blades, the faster the vessel, however, this rule is not cast in stone. The deciding factor will always be the particular application the boat is used for in order to determine the number of blades required to achieve the best engine performance.
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Long Lasting Ultracoat Powder Coated Finish
Exclusive to Turning Point, the Ultracoat powder coat rivals a fineautomotive finish, and is more durable than paint. Utilizing a state-of-the-art five step process, Ultracoat gives the propeller a shiny,uniform appearance that enhances any boat’s good looks. This is theGold Standard in Aluminum Corrosion Protection. Prop looks Newer Longer! Compared to Competitors’ 4 step Paint and Coating Processes that result in much less abrasion and corrosion resistance.
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How Does Inboard And Outboard Propellers Work
In most cases, inboard or outboard boat propellers for sale are described using two numbers. The numbers are an indication of the pitch and the diameter.
Usually, the outboard and inboard boat propellers for sale comes with a hub that has blades all around. These blades bear the same size and length. They are also twisted to make it possible for them to actually push the water back as they rotate. The action of pushing water is what the boat moves forward .
In most cases, propellers blades rotate clockwise if you are looking from the rear side. There are also the anticlockwise ones that are paired with the clockwise ones if your boat has a dual-engine installation. This can help to stabilize the boat and make steering easier.
You can buy boat propellers according to blade such as 3 blade stainless steel propellers, 4 blade stainless steel boat propellers according to your boat needs.
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Props: Folding Propellers Vs Feathering Propellers
- Original: Oct 24, 2013
Would you buy an automobile whose rear brakes locked up and dragged along the road when going downhill? Not likely. So why do so many sailboat owners do much the same thing by dragging the blades of a propeller through the water behind them when the engines off?
A fixed propeller can create a considerable amount of drag when sailing. A three-blade fixed prop could reduce your boats speed by as much as 20 percent. For a medium-sized cruising boat, that might be a loss of between 0.6 and 1.2 knots under sail. Put another way, it could add an hour to a 20-mile daysail.
Theres also the interminable debate as to whether you should let the prop rotate while sailing, with all the associated noise and stern gland and transmission wear that incurs or whether you should stop it from spinning by putting it in gear, which might harm the bearings in some types of transmission. Tests have proven that a spinning prop usually creates less drag than a static one, but if youre planning any long passages it still might be advisable to fit a shaft brake.
Faced with these kinds of choices, why not cut right through the Gordian knot they present and install a propeller that either folds or feathers?
Stainless Steel Propellers Vs Aluminum Or Plastic
Most boat propellers are going to be one of these three materials. Aluminum props tend to be the most common. They are lighter and cheaper and can do a great job. However, stainless is definitely stronger. Stainless is also able to have thinner blades. If you want a top quality boat propeller, stainless steel is probably what you want. Most boats come with aluminum propellers. Large boats like yachts and small fishing boats alike.
Plastic props are more common on small boats. They require less power and the prop will do less work. The propeller blade on a plastic prop is going to be flimsy, as you might expect. Heavier boats cant use these. Theyll have more drag than the prop can handle.
For optimum performance, stainless steel props are best. The boats performance will reflect this. However, you may see increased fuel efficiency with a lighter aluminum prop. Much of it depends on the type of boat and engine you have.
Basically, a stainless steel prop is going to last longer than the others. Up to five times longer, in fact. It can stand up to more abuse. Youll be less likely to need to replace it as soon as another type.
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Your Boat Seems Slower
There’s nothing wrong with wanting a little bit more speed for your boat. There are times when your propeller is in good working condition, but you need to upgrade your gear. Your dream is to zoom across the water, not sputter along behind everybody else.
In that case, you need to find stainless steel boat propellers for sale. These will add about three knots. Sure, this isn’t a sign of damage, but there’s nothing wrong with wanting to take it up a notch.
How To Use The Boat Prop Calculator Tool
Knowing the theoretical speed for your boat can help you select the proper pitch. To use our boat prop calculator, you need four inputs:
- RPMs: Revolutions Per Minute. Enter the high end of the operating range established by the engine manufacturer or the maximum RPMs you can attain with your current propeller. The recommended operating range should be listed in your owners manual and can also be found online.
- Pitch: This is the theoretical distance the propeller would travel through the water with each revolution . Think of a screw going through wood. It is often stamped on the outside of the propeller. In this example, the propeller has a 24 pitch.
- Gear Ratio: This is the number of drive shaft revolutions for one revolution of the propeller. You can find this in your owners manual or by searching online.
- Prop Slip: This is the relationship between the actual vs. theoretical distance your boat travels with each revolution of the propeller and is impacted by the hull design, weight of your boat, propeller design and other factors. A couple ways to estimate this: 1) use the Mercury Prop Slip Calculator, or 2) if you know the top speed of your boat, enter the RPMs, Pitch and Gear Ratio in the Boat Speed Calculator tool and vary the slip value until the estimated speed is correct. For example, I have a boat with a max RPM of 5,800, my propeller pitch is 24 and the gear ratio is 1.92. Based on these inputs, a Prop Slip of 13% gets me to my correct maximum top speed of 60 mph.
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Signs You Should Replace Your Boat Propeller
You don’t want to wait until you’re out in the water to find out something is wrong with your boat propeller. After all, this is an integral part that helps propel the boat. If it’s damaged or worn out, it can put you in a dangerous scenario.
If you’re new to boating or unsure of what to look out for when it comes to replacing the propeller, you’re in luck! This guide will go through the ten major signs that it’s time to replace your boat propeller.
Let’s get started.
Is It Time To Replace Your Boat Propeller
The reality is that without a boat propeller, you can’t use your boat.
You already invested so much into your boat. Having routine inspections and keeping it in great shape will ensure that it lasts you for years to come. If you believe that it’s time to replace the propeller but aren’t sure, these signs are sure to help guide the way.
If for any reason you still don’t know for sure, there are plenty of resources to check out. The important thing is making sure your boat is good to go and safe to use!
Is it time to replace your boat propeller? Take a look at our products and have your boat looking good as new.
How Does The Pitch Of The Propeller Affect The Boats Performance
It is very well known that every change in propellers pitch has a direct effect on the performance of our boat. It is also known that each inch of the pitch «costs» 150-200 rpm for our engine at WOT, a relationship inversely proportional.
As the pitch increases, the load on the engine increases too, since the propeller «grips» a larger amount of water, leading this way to the reduction of its rpm. The reverse happens when we decrease the pitch.
To determine the effect of the propellers pitch on the boat’s performance as accurately as possible, we tested three exactly same propellers, the only difference of which is the size of their pitch, on a Suzuki 300hp which was mounted on a 930 Marvel rib.
The tests were made with the 3-blade propellers of Suzuki, the pitchs size of which was 18.5, 20 and 21.5, at the same time, in the same sea area and of course with the same loads.
Looking at the above tables we see that as the pitch of the propeller increases:
- the cruise speed at 4000 and 4500 rpm increases by 2 knots per each 1.5 inch of pitch. With the 18.5 pitch propeller our speed is 26 knots at 4000 rpm, with the 20 pitch propeller our speed is 28 knots while with the 21.5 one our speed is 30 knots at the same rpm
- the engines rpm reduces at WOT
- the acceleration gets slower and thus the throttle response reduces
- the slippage increases at the whole rpm range
- the time to plane gets longer and the boat stays on plane at higher speeds and more rpm.
Should I Repair Or Buy A New Boat Propeller
Most small dings or bends in an aluminum prop can be repaired for a reasonable price. If you do repair, make sure the shop does not file down the blade edges thereby reducing diameter. If your damage includes bites or chunks out of the blade, you should consider a new prop.
Keep in mind that while aluminum propellers can be welded back to look like new, there is significant strength loss when you do. Since a light tap could then put you back where you started from, you shouldnt spend money on an expensive repair. Stainless props cost more to repair than aluminum because the material is more difficult to work with, however, once properly repaired, they can be almost as good as new.
Another option is Piranha propellers they were developed with three things in mind: durability, performance and affordability. A key feature is that the blades are replaceable. You can change the diameter and the pitch, save on the costs involved with propeller repairs, not to mention the potential damage to your gear case. With Piranha you can have some spare blades in the boat for a quick and affordable repair.
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Tips For Knowing When To Replace Boat Propellers
How can you tell if your boat propeller requires replacement? There may be an obvious reason for doing so such as if your prop has sustained visible damage to a blade. However, even when your propeller is performing within manufacturers recommended guidelines, often there is room for performance improvement. Reasons for replacement include:
Close inspection reveals broken or cracked blades. Upgrade to different materials such as aluminum or stainless steel. Upgrade to a different number of blades, from 3 to 4 for example. Upgrade to a larger size boat propeller to improve acceleration and top end performance. Want to carry a replacement propeller on board just in case.
Squeeze Cast For Added Strength
Stainless steel performance is built into the Hustler Aluminum prop line.This is achieved through unique blade geometry and an exclusive TurningPoint manufacturing process, Squeeze Casting. This process generates the highestmechanical properties attainable in a cast aluminum prop resulting from high density tighter grain structure. Stiffer blades means less flex and a faster prop.Competitors’ Aluminum propellers are manufactured utilizing old Die-Cast process that produces props with air bubble, voids, and granularity. Weak, lack of strength and stiffness. Difficult to repair.Blades Flex under load, inefficient, loss of propulsive efficiency.
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Is A Stainless Steel Prop Always The Best Choice
Many people think a stainless steel propeller is always the best choice. But for a lighter and smaller boat, that may not always be the case. As you saw, many aluminum props are extremely high quality. Aluminum props can deliver better hole shot and increase speed. They give great fuel economy and have a wide pitch range. Whether you want a lower pitch or something higher, an aluminum prop could work fine.
The other big consideration is price. Aluminum props are cheaper. That price difference can be very significant.
The Best Boat Propellers Material
When picking new or used boat propellers, you need to think about the material. Outboard propellers for sale can be made from stainless steel or aluminum.
If you are looking for new or used boat props for sale, you can look at our wide selection at Harbor Shoppers. You can find high quality new and boat propellers for sale at affordable prices.
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How To Choose The Correct Pitch And Blade Count
Before you dive into choosing a propeller, understand your boatâs intended use. Consider your average speed, load, and boating location. If you will be using the boat for multiple applications, you may need to switch props. The propeller choice directly affects the engine RPM and therefore its performance. Choose a propeller that puts the engine RPM at the midpoint or higher of the wide open throttle range with a normal load. This operating range will translate to the highest horsepower available from your outboard. Refer to your engine operating manual for the operating range.
Once you know the operating range, consult the propeller guide for your engine to pick a combination of pitch, blade number, and material. Choose a range of propellers to perform a water test. Test the props under the same conditions that you would typically use the boatâsame load, gear, and water. Set the trim angle so the boat has optimum speed on top of the water.
To test the prop, run the boat at WOT and observe the maximum engine RPM on a tachometer. If the RPM is below the recommended operating range, switch to a propeller with lower pitched blades. If the RPM is higher, switch to a propeller with higher pitched blades. Each inch of pitch size will change the RPM by 150-200 RPM. Aim for the midpoint or higher of the recommended operating range. Keep in mind that high altitudes will reduce engine power, so choose a lower pitch to achieve the same RPM as on sea level.