Boat propellers have a long history that dates back to the early days of marine propulsion. Boats used to be propelled by sails, oars, or simple paddle wheels until the propeller was created. Leonardo da Vinci created a screw-type paddle wheel for use in a boat in the early 16th century, which is the first time that a screw-type propulsion system is known to have been used.
But, the modern boat propeller was not created until the 19th century. The first patent for a boat propeller was submitted by French engineer Henri-Joseph d’Estournelles de Constant in 1835. This concept involved a rotating screw that could move a boat ahead when driven by an engine.
The design of boat propellers was refined during the following decades, including the advent of multi-bladed propellers, which offered higher efficiency and better maneuverability. Propeller use as the principal method of propulsion for boats increased significantly after the internal combustion engine was developed in the late 19th century.
In the 20th century, improvements in materials science and manufacturing methods allowed for the creation of boat propellers that were more effective and long-lasting. Propeller design could be optimized for particular boat types and uses thanks to the development of computer-aided design and manufacturing technology. Boat propellers are now a necessary part of almost all boats, from little recreational craft to massive commercial ships.
Did you know that recreational boating contributes $170.3 billion to the US economy each year? Or that 2018 marked the seventh consecutive year that boat sales have gone up in the US? Boating has long been part of our recreational and pop culture with great songs like Rock the Boat by Hues Corporation and so many others.
All these show that folks in the US are getting back into the water. After all, boating, whether for food or fun, has shown to have positive effects on our health. In fact, 72% of people say they feel healthier after spending time out on the water.
That said, if you’re planning to get your own boat, it’s best that you nail the basics of a boat propeller first. It may always go unseen, but it’s this part that makes a water vessel move in the water in the first place. The last thing you want is to be in the middle of deep waters because of a failed boat prop.
Ready to learn all about the common issues that affect boat propellers and what you should do if you run into them? Then let’s get right into it!
Damaged Blades
Cracks, dents, nicks, and warping on prop blades can all result from direct hits with objects. Bottoming out, getting too close to rocks, or hitting sand bars are the top reasons for these damages. A fishing line or towrope may also have snarled the shaft and “pinched” a blade on the prop.
Either way, they can all lead to your boat vibrating excessively and becoming out of balance. You may also feel that your prop pitch rate has gone down, making it harder to accelerate in the water. In some cases, damaged blades may also affect the boat’s overall engine performance.
Clogged Prop Hub
Weeds, as well as fishing lines, especially those made of monofilament, can clog the prop hub up. Your boat prop, however, is more likely to get clogged by microplastic. After all, about 14 million tons of this material finds its way into the world’s oceans every year.
The more debris there is in the hub, the lower your boat’s performance will be. Ignoring the problem can result in permanent damage to both the propeller and the engine.
Corroded Blades
Corrosion is a natural process that makes metals turn into that reddish thing we call “rust”. This happens when metals come into contact with substances such as dirt and bacteria. It also occurs when refined metals react with electrical current, oxygen, and hydrogen.
All these corrosive elements are in the water, be it fresh or seawater. We call the corrosion that affects water vessels as “marine corrosion”. Marine corrosion takes many forms, including simple, electrolytic, galvanic, and crevice corrosion.
To prevent this, manufacturers use corrosion-resistant alloys in their products. These include aluminum, copper, bronze, galvanized steel, stainless steel, and carbon steel. Their resistance varies though, with stainless steel props often having the highest resistance.
To further keep corrosion at bay, these propellers undergo a special finishing process. This involves coating them with chemicals designed to increase marine corrosion resistance. They then pass through an electrochemical process, giving them an anodized hard coat.
Unfortunately, corrosion can still occur when these metals sustain physical damage.
Let’s say your aluminum prop hits another ferrous metal floating in seawater. This can lead to a dent that, if left untreated, will worsen into a full-blown crack or crevice. Salt and other substances can then get into the damage, eating away at your propeller.
Microbiological Formations
Speaking of substances, did you know that about 80% of wastewater gets dumped into the ocean each year? Worse, a huge percentage of this wastewater doesn’t undergo proper treatment. Aside from the pollution they cause, they also trigger large microbiological blooms.
Many of these blooms take the form of algae, which can foul up your boat’s propeller. Other causes of fouling are tubeworms and barnacles. All these can settle on any submerged surface of your boat, and not only on your prop.
The more marine growth on your propeller, the more excess weight that piles up on it. Over time, this will cause a significant reduction in your prop’s performance. Ultimately, your boat’s engine will also suffer.
Moreover, these tiny creatures become harder to get rid of the longer you allow them to remain on the prop.
Worn Blades
Age does contribute to wearing on propellers, but it’s more often due to a lack of maintenance. Ignoring problems that require immediate repairs can also wear your prop blades faster.
Poor steering and piloting behavior are also common culprits behind early prop failure. There’s also the material, brand, and make of prop that you have on your boat.
Either way, if your prop rarely sees cleaning and servicing, it will wear down and out sooner. You won’t notice it right away, but your ride will continue to slip, slow, and ultimately, break down.
Unfortunately, if this happens, you may end up stranded in the middle of the water. Such events are common in the US, contributing to the almost 20,000 rescue cases done by the US Coast Guard each year. In fact, machinery failure was the fourth main reason for boating accidents in the US in 2018.
What to Do If Your Boat Propeller Is Failing You
If you’ve noticed any change to your boat’s speed and overall performance, it’s time to check your prop. However, since it’s in the water, you need to properly mount your boat on dry land first.
This way, you can elevate the propeller so that it sits within the eye level. This will let you inspect the prop better and also give you easy access to its removal and repair.
Also, since you’d need to completely remove the prop, be sure to shut down your boat’s power supply. Take the battery leads off and disconnect all wires before detaching the prop. This will help protect you from injuries that a prop-gone-rogue may cause.
Once you’ve done all these, you can now detach the prop by removing all its fasteners. It’s important to take off all the nuts, bolts, and screws one by one. Otherwise, you run the risk of denting or even cracking the blades by missing a fastener.
Prepare yourself for some serious lifting too, as propellers are quite heavy. If possible, have someone else assist you throughout this entire process.
Getting Minor Dings Out
If your propeller only has a minor ding, you may be able to fix it using two adjustable wrenches. Use one wrench to hold down and secure the blade adjacent to the damaged area. Use the other to slowly but firmly raise the dinged area until it’s as level as possible.
In case the ding or dent is too big and deep though, it’s best to send it to a prop shop. If you apply too much pressure, it can cause the entire blade to tear or even split.
Filing Down Small Burrs or Nicks
Burrs usually occur when the edge of the prop blades rotate through the sand. Nicks often develop when the blades hit an object hard enough to chip away at metal. In both cases, you may be able to file them down, so long as they’re only minor.
Keep in mind that excessive grinding can result in the affected blade becoming “too short”. This can then lead to the entire prop becoming out of balance. So, if the damage requires extensive filing, you should send the prop to a repair shop instead.
When Repairs Won’t Cut It
Sometimes, serious propeller damages aren’t worth their repair cost. Especially if there’s a lot of cracks, major pitting, or if a blade’s missing.
You should also consider the age of your propeller. If it’s been a decade or more, then it may be time to fit your boat with a new, better-performing prop.
Factor in the material of your existing propeller and the frequency of your trips too. Let’s say that you have an aluminum prop, which is fine for once- or twice-a-year trips. If you plan to take out your boat more often though, the repairs may not be enough to make it last longer.
Don’t Delay Getting Your Propeller Fixed
There you have it, the ultimate guide on boat propeller problems and some of your best DIY repair options. What’s important is to never put off prop repairs. The longer you leave those cracks and dents untreated, the worse they will become.
For bigger prop problems, it’s best to leave them in expert hands. Better yet, invest in a new propeller, especially if the one you have has seen better years. Not only will a new prop help your boat become energy-efficient again—it’ll also be better for your safety.
Any kind of boat propeller can malfunction, but some propellers are more prone to specific kinds of issues than others. Some of the frequent problems with various propeller types include:
- Fixed Pitch Propellers – The most fundamental kind of propellers have a single blade with a fixed angle of attack. These are known as fixed pitch propellers. These propellers are not very efficient and can have limitations when handling high speeds or big loads, despite being reasonably straightforward and affordable.
- Adjustable Pitch Propellers – Propellers with adjustable pitches are more complicated than those with set pitches since they include many blades that may be changed to alter the angle of attack. Although these propellers are more effective than fixed-pitch propellers, they are also more costly and need more upkeep.
- Controllable Pitch Propellers – The most modern sort of propellers are those with controllable pitch, which have numerous blades that can be changed in real time to maximize effectiveness and performance. These are the most effective and adaptable propellers, but they are also the most expensive and need the most upkeep.
Conclusion
You can quickly diagnose and solve many typical boat propeller faults by adhering to these easy procedures for fixing boat propellers. However, it’s always advisable to seek the help of a qualified boat technician if you’re concerned about performing the repairs yourself or if the issue is more complicated.
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