AO Smith B855 2 HP Square Flange Motor Review: The Heart of a Healthy Pool?

There’s a specific sound that strikes a particular kind of dread into the heart of every pool owner. It’s not the splash of a cannonball or the laughter of a summer party. It’s the sound of silence when there should be the gentle hum of circulation. Or worse, the grinding, whining protest of a motor on its last legs. I remember the morning it happened to me. The familiar, reassuring drone of my Pentair Whisper-Flo was gone, replaced by a strained, intermittent buzz followed by a decisive click from the breaker. A quick inspection confirmed my fears: the motor was shot. The immediate vision was of a crystal-clear oasis slowly turning into a murky green swamp, followed by the even more terrifying vision of a four-figure repair bill from a pool company. This is the critical juncture where many pool owners find themselves, facing a choice between a costly full pump replacement or the much more economical path of a DIY motor swap. It’s for those in this exact predicament that a product like the AO Smith B855 2 HP Square Flange Motor becomes not just a part, but a lifeline.

What to Consider Before Buying a Replacement Pool Motor

A replacement pool motor is more than just an item; it’s a key solution for restoring the circulatory and filtration systems that are the literal heart of your swimming pool. Without a functioning motor, your pump cannot pull water through the skimmers, push it through the filter, and return it clean and sanitized. This leads to stagnant, unsafe water and a potential algae bloom that can be difficult and expensive to remediate. The primary benefit of a replacement motor is economic. It allows you to salvage the perfectly good “wet end” of your pump—the durable plastic housing and impeller—while only replacing the component that has failed, saving you hundreds of dollars compared to a complete pump unit replacement. You can check the latest price and availability to see just how significant these savings can be.

The ideal customer for this type of product is someone with a moderate level of DIY confidence who owns a compatible in-ground pool pump, such as a Sta-Rite, Hayward, or Pentair model that uses a 56Y frame and a square flange connection. They are facing a motor failure and are willing to invest a couple of hours of their time to perform the replacement themselves. This motor might not be suitable for those who are completely uncomfortable with basic electrical wiring (specifically for a 230V appliance) or those whose entire pump housing is cracked or damaged, necessitating a full pump replacement. For owners of smaller, above-ground pools, a dedicated all-in-one pump system would be a more appropriate choice.

Before investing, consider these crucial points in detail:

• Dimensions & Space: The single most important factor is compatibility. The AO Smith B855 2 HP Square Flange Motor features a 56Y frame and a square flange mount. You must verify that your existing pump’s wet end is designed for this specific configuration. Measure your bolt pattern and check the label on your old motor; a mismatch here means the new motor simply will not attach.
• Capacity/Performance: This is a 2 horsepower (HP) up-rated motor. “Up-rated” means the motor has a lower service factor (typically 1.0 to 1.25) compared to a “full-rated” motor of the same HP, but it’s designed to deliver the stated horsepower under load. A 2 HP motor is suitable for larger in-ground pools, pools with attached spas, or systems that include water features like waterfalls or deck jets that require higher flow rates to operate correctly.
• Materials & Durability: Look for quality construction. This motor features durable copper windings, which are superior for heat dissipation and efficiency compared to aluminum. The outer shell is described as “corrosion-resistant,” a vital feature for a piece of equipment that often lives in a humid, chemical-adjacent environment. Long-term durability is the goal, protecting your investment from the elements.
• Ease of Use & Maintenance: The primary “use” is the installation process. Look for features that simplify this, such as easy-to-access wiring compartments and clear connection terminals. Once installed, maintenance is minimal, mainly consisting of ensuring the motor’s ventilation ports remain clear of debris to prevent overheating and occasionally checking for bearing noise, which can indicate wear over time.

Investing in the right replacement motor can bring your pool back to life efficiently and affordably. It empowers you to take control of your pool’s health and your wallet.

While the AO Smith B855 2 HP Square Flange Motor is an excellent choice for a direct replacement, it’s always wise to see how it stacks up against the competition and understand the broader market. For a broader look at all the top models, including full pump systems and specialized units, we highly recommend checking out our complete, in-depth guide:

First Impressions: A Heavyweight Contender Arrives

Unboxing the AO Smith B855 2 HP Square Flange Motor immediately gives you a sense of its robust construction. At over 30 pounds, this is no lightweight plastic component; it feels solid, dense, and built for a singular, powerful purpose. The black, corrosion-resistant finish is smooth and professional, and the Century Electric branding (the successor to the A.O. Smith name in this space) is cleanly applied. Holding it in my hands, it felt like a worthy successor to the original motor that had served my pool for nearly a decade.

Two things stood out immediately. First, the threaded shaft was perfectly machined and protected by a plastic cap, ready to receive the pump’s impeller. Second, the rear access panel for the wiring was noticeably more spacious than on many older models. This was a welcome sight, as anyone who has fumbled with wires and wire nuts in a cramped motor housing can attest to the frustration it can cause. It was a clear design improvement, something echoed by users who’ve upgraded from older Centurion motors. It arrived looking ready for business, a heavy-duty component promising to restore the powerful flow my pool system was missing. You can see its full feature set and detailed specifications online.

Performance Deep Dive: The B855 Under the Microscope

A replacement motor lives or dies by its performance in three key areas: the ease of installation, its raw power and efficiency, and its long-term durability. We put the AO Smith B855 2 HP Square Flange Motor through its paces, combining our hands-on experience with extensive user feedback to build a complete picture of this workhorse motor.

Installation and Compatibility: A Manageable DIY Project

The number one reason to buy this motor is to replace a failed one, so the installation process is paramount. Our experience aligns perfectly with the consensus from seasoned users: the physical installation is straightforward, but the wiring requires careful attention. The process begins with killing power at the breaker—a non-negotiable safety step. Separating the old motor from the pump’s wet end involves removing a series of through-bolts. As one user noted, “taking the old one out could be a Challenge,” especially if the bolts are corroded. A little penetrating oil and patience are your best friends here.

Once separated, the most delicate part of the job is removing the impeller from the old motor’s shaft and, crucially, replacing the pump shaft seal. We cannot overstate this: always install a new shaft seal. It’s an inexpensive part that prevents leaks that will destroy the new motor’s bearings. Attaching the AO Smith B855 2 HP Square Flange Motor to the wet end was a perfect match for our Pentair Whisper-Flo housing. The square flange lined up precisely, and the bolts went in smoothly. This seamless compatibility is a major selling point and a huge relief mid-project.

Then comes the wiring. One user rightly praised Century for making improvements that make the wiring compartment “easier and not so cramped.” We wholeheartedly agree; there is ample room to work. However, another user’s warning about unclear wiring instructions is also valid. The diagram on the motor’s label is technically correct but can be confusing if you’re not familiar with electrical schematics. For a 230V setup, you connect your two hot lines (typically L1 and L2) to the designated terminals and the ground wire to the green ground screw. The key is ensuring you are connecting for the correct voltage and rotation. My advice: take a clear photo of your old motor’s wiring *before* you disconnect anything. As one user did, documenting your setup is the best way to ensure you get it right. Despite the learning curve on the wiring diagram, the actual installation took us about an hour, saving hundreds in labor costs and representing a huge win for the DIY-inclined pool owner. This direct-fit compatibility is a feature that really sets it apart for owners of major brand pumps.

Power, Flow, and Circulation: The 2 HP Difference

Once the breaker was flipped back on, the difference was immediate. The AO Smith B855 2 HP Square Flange Motor spun to life with a confident, low-frequency hum. The silence was broken, but this time by the sound of a healthy, powerful system. Within seconds, the pump was fully primed, and water was surging through the pipes. The power of a 2 HP motor is not just a number on a spec sheet; it’s visible in the pool. The surface skimmers, which had become lazy with the old, dying motor, were now creating powerful vortexes, aggressively pulling in leaves and debris. The pressure gauge on our filter jumped to a healthy operating PSI, indicating strong flow through the system. For pools with water features, this kind of power is essential. It can mean the difference between a trickling waterfall and a beautiful, cascading sheet of water.

This motor is classified as “up-rated,” which is an important distinction. In simple terms, it means it’s built on a frame that might typically house a 1.5 HP full-rated motor but is engineered to deliver a true 2 HP at its peak. For the average residential pool, this provides more than enough power for excellent circulation, ensuring chemicals are evenly distributed and that the entire volume of water is turned over and filtered multiple times a day. We found its performance to be rock-solid, effortlessly handling the demands of a 25,000-gallon pool with an attached spa. The powerful circulation it provides is the foundation of a clean and clear pool, making this motor an excellent investment in your water quality. You can find out more about its performance capabilities here.

Acoustic Signature and Durability: Quiet Strength Built to Last?

One of the most pleasant surprises was the motor’s sound profile. Several users described it as “quiet” or “super quiet,” and we concur. Compared to the whine of the old motor, the B855 produces a smooth, consistent hum that fades into the background noise of the yard. This is a significant quality-of-life improvement, allowing you to enjoy the peace of your backyard without the constant drone of loud machinery. As one user perfectly put it, “It keeps the 27 year old Pentair Whisperflo pump running as quietly as new.”

Durability is the million-dollar question for any pool motor. This is where user experiences paint a slightly more complex picture. On one hand, we have multiple accounts of extreme longevity. One user replaced an identical model that had worked for over 10 years. Another had a previous Centurion motor that was completely submerged during a hurricane and continued to run for years afterward. This speaks to a legacy of rugged, reliable engineering. However, it’s crucial to address the outlier report from a user whose motor failed from corrosion in under two years. While the motor is labeled “corrosion-resistant,” no motor is corrosion-proof. Factors like ambient humidity, proximity to saltwater, and improper chemical storage can drastically shorten a motor’s life. Our assessment is that the AO Smith B855 2 HP Square Flange Motor is built on a very reliable platform with a history of durability, but its ultimate lifespan is also dependent on proper installation and its operating environment. Ensuring it has adequate ventilation and is protected from direct water spray is critical for long-term health. The overwhelming evidence points toward a reliable workhorse, making it a dependable choice for your pool’s heart.

What Other Users Are Saying

Synthesizing feedback from a wide range of owners reveals a clear and consistent picture of the AO Smith B855 2 HP Square Flange Motor. The vast majority of praise centers on its performance as a direct replacement. Users frequently comment on how it brought their old, reliable pump housings, like the Pentair Whisper-Flo, back to life. The quietness of the motor is its most celebrated feature, with many expressing surprise at how much of their old pump’s noise was coming from the failing motor itself. The sentiment of having “saved hundreds” by doing the installation themselves is a recurring theme, highlighting the product’s immense value proposition.

On the critical side, the most common piece of feedback involves the wiring instructions. While experienced users find it manageable, several novices expressed anxiety and confusion, stating, “the wiring instructions are not clear.” This suggests that while the motor is excellent, the documentation could be improved for a broader DIY audience. The most serious negative feedback comes from a user who experienced a corrosion-related failure after just 1.5 years, a stark contrast to the many reports of 8-10+ years of service. This serves as a critical reminder that while the product is generally robust, it is not immune to harsh environmental conditions or potential manufacturing defects.

How Does the AO Smith B855 Compare to the Alternatives?

The AO Smith B855 2 HP Square Flange Motor is a specific solution—a replacement motor—for a specific problem. It’s important to understand how it differs from other products in the broader pool pump category, which often serve entirely different needs.

1. Doheny’s 1.5 HP Pool Pump

The Doheny’s unit is a complete pump assembly (motor and wet end included) designed specifically for above-ground swimming pools. This is the key distinction. You would choose this product if you have an above-ground pool and your entire pump unit has failed or if you are installing a new pool. With 1.5 HP, it’s slightly less powerful than the B855, which is appropriate for the smaller water volume of most above-ground pools. If you own an in-ground pool and only your motor is broken, the Doheny’s pump is not the right choice; the B855, which allows you to keep your existing plumbing and wet end, is the far more targeted and economical solution.

2. Bestway Flowclear 1500 GPH Filter Pump

The Bestway Flowclear exists in a completely different universe from the B855. This is not just a pump but an integrated, low-power pump and filter system designed for small, storable above-ground pools (like those from Intex or Bestway). Its flow rate is measured in gallons per hour (GPH), not horsepower, highlighting its much smaller scale. This is an entry-level, all-in-one solution for pools up to about 8,400 gallons. It is in no way an alternative to the B855, which is a heavy-duty component for permanent, in-ground pool systems that are thousands of gallons larger and require vastly more power.

3. Little Giant LG-APCP1700 1/3 HP Automatic Pool Cover Pump

The Little Giant pump serves a completely different, yet essential, function for many pool owners. This is a submersible utility pump designed to be placed on top of a solid pool cover to automatically pump off accumulated rainwater and snowmelt. Its job is to protect the cover from damage, not to circulate or filter pool water. It has no connection to the pool’s main plumbing system. Therefore, it isn’t a competitor to the B855 at all. A pool owner might own *both* products: the B855 to run their pool in the summer and the Little Giant to protect their cover in the winter.

Our Final Verdict: Is the AO Smith B855 the Right Motor for You?

After extensive testing and analysis, our conclusion is clear: the AO Smith B855 2 HP Square Flange Motor is a top-tier choice for the pool owner with a failed motor on a compatible in-ground pump. Its value proposition is outstanding, offering the power, quiet operation, and reliability of a professional-grade component at a price that allows for significant savings through DIY installation. It successfully carries on the rugged legacy of the A.O. Smith brand, providing a direct-fit solution that can restore a high-end pump to like-new performance.

We recommend it specifically for the DIY-savvy individual who is comfortable with basic plumbing and electrical work. Its only notable weaknesses—the slightly opaque wiring instructions and the isolated concern about corrosion—are manageable with careful preparation and proper environmental protection. If your pool has gone silent and you’re facing a hefty repair quote, don’t replace the entire pump. Give your trusted system a new heart. The B855 is a powerful, quiet, and cost-effective solution that will get your water moving and restore your backyard oasis. For anyone in this situation, this motor is a highly recommended purchase. You can check the latest price and get your pool running again here.