Debunking Myths & Better Understanding Sea-Doo’s Carbon Ring Seal

The haters. Oh boy, the haters. If the internet has taught us one thing, it’s that people sure love to dump on stuff. For anyone who spends any time online, they’ll find that the trash talk between brand-loyal watercraft enthusiasts is roiling at a fever pitch. Barbs are freely exchanged, but when it comes to Sea-Doo, one jab rears its ugly head more than any other: they sink. And if you were to believe what the digital mob preaches, it happens all the time.

So if we are to believe that these machines sink more often than a lead-filled, mesh-bottomed canoe, why is it that Sea-Doo has the largest slice of the marketplace; or some of the highest customer satisfaction; or the largest segment of returning customers than any other brand? Could it be the haters are wrong? *gasp!* Well, we won’t say “wrong”, but we will say that there is a lot of misinformation floating out there, and quite a bit that’s simply missing from the public dialogue.

Now that we’ve got you all roiled up and triggered, let’s dive into the meat of the story. In this essay, we’re going to address the primary cause of most of these rumors, these uniquely rare and isolated experiences, and more importantly, how to make sure it never happens to you.

The subject in question is Sea-Doo’s carbon ring. This ring encircles the driveshaft prior to it exiting through the hull and into the pump, sealing the hull from the water outside. The two-piece design provides the craft a waterproof seal while allowing the shaft to spin with the least resistance (ie. friction) possible. More pertinent to the focus of this discussion, the carbon ring is a wear item, just like the wear ring in the pump. It is not designed to last forever.

When under optimal conditions (correctly installed, operated and serviced), a carbon ring can last upwards to 100-to-150 operating hours. Yet, we find more often than not, premature failure of the carbon ring directly linked to operator error, misuse and damaged equipment. Thankfully, there are several telltale signs to alert a Sea-Doo owner well before a catastrophic failure – that is, between the watercraft’s regular service intervals.

The first cause for potential carbon ring failure is also the most common – and gratefully, the easiest to avoid: excessive heat. While not in direct contact to the driveshaft, the carbon ring caps the bellows (the corrugated black rubber boot that contains the shaft’s ball bearing) that encloses the shaft. The carbon ring is preloaded against a tapered, machined support ring (ie. hat), which is held in place on the shaft by a keyed circlip. It’s the carbon ring pressing against the hat on the driveshaft that makes the watertight seal.

As the driveshaft spins, so does the hat – with its flat machined surface – pressed against the stationary carbon ring. This of course, generates friction. Friction causes heat, and excessive heat often leads to early failure. The carbon ring is only cooled when the Sea-Doo is in the water – whether idling or at speed. The heat generated by the hat’s surface spinning against the face of the carbon ring can lead to premature wear (and failure) when operated too long out of the water.

Sounds pretty simple, right? Well, not so when you see folks revving the snot out of their Sea-Doo on the trailer. Even when flushing the exhaust system with a running hose, the carbon ring is not being cooled. That is why the operation and service manual recommend running the engine no more than 90-seconds out of the water. Even “blipping” the throttle hard enough to purge the waterbox can lead to premature wear and failure.

While a bent or injured impeller blade can cause undue and aggravating turbulence, the unsettling harmonic is more likely to radically deplete the longevity of the pump’s wear ring before injuring the carbon ring – primarily because the carbon ring is only making contact with the hat, and not the shaft itself. Yet, a bent driveshaft oscillating at several thousand revolutions per minute can carve an erratic wear pattern into the carbon ring’s face, eventually leading to an early failure – although this is often the least likeliest cause.

Although not common, bending or distorting a driveshaft can happen due to careless operation; either by sucking up a tightly coiling a rope; or impact with rocks, branches or other objects small enough to pass through the intake grate. Even when poorly maintained or with parts improperly installed it is difficult to damage a driveshaft enough to injure the carbon ring.

The final factor linked to carbon ring failure is often its hardest to diagnose; engine misalignment. First and foremost, it is incredibly rare that an engine come from the factory misaligned; and all damages would be rightly covered by BRP’s warranty. Rather, it is more likely that engine misalignment is the byproduct of either harsh impacts from wave jumping or having had the engine out before.

Contrary to popular belief, these high-powered machines are not designed to jump waves, and doing so rapidly weakens, loosens and often breaks engine mounts. During a particularly severe impact, the driveline undergoes extraordinary torsional forces, causing the engine to literally shift. It might be significant (in the form of a broken motor mount) or minor, but a misalignment has potentially occurred.

Many times, such riders have replaced broken or worn motor mounts presuming that aligning the bolt holes would return the driveline to its proper default position. Not so! Certified BRP mechanics will have the correct alignment tools to ensure that the driveline is square. The same goes for the aftermarket tuner or the less-than-reputable repair shop who misaligned the engine upon reinstalling it. Both of which, the onus lies with the owner, not BRP.

Because the carbon ring is the final line between having a great day out on the lake or sinking to its bottom, it’s best to 1. maintain a proper service inspection schedule with your dealer or certified mechanic; 2. look for signs of wear in the form of excessive water in the engine compartment (particularly around the bellow), water whipping violently around the bellow, or large deposits of fine dark gray carbon blown or streaked across the engine compartment; and 3. to consider upgrading your carbon ring kit.

The Watercraft Journal spoke with Greenhulk PWC Performance‘s own Jerry Gaddis, who recommended upgrading to the new style carbon ring hat. Jerry explained, “The new carbon seal hat is 5mm thicker. That means its putting more tension on the carbon ring for a better seal. The kit is less than $90 bucks and comes with the new thicker hat and a brand new carbon seal. It’s the cheapest insurance policy you can get.”

So no, Sea-Doo’s don’t sink; but poorly maintained or incorrectly operated Sea-Doos with worn out carbon rings can though. Proper use and regular service from certified technicians will ensure your Sea-Doo will continue to perform as the day you first picked it up from the dealership; it’s really that simple. And for the haters online? There’s not much you can do about those miserable saps but sit back and feel sorry that they’re not having as much fun as you are.

Addendum (8.24.20): There have been a rash of carbon ring seal failures in recent years as noted by increased service requests. According to The Watercraft Journal’s sources, a confluence of weak or porous materials used by outside suppliers and a limited sequence of units manufactured with slight engine misalignment have contributed to premature failure of carbon ring seals. To our knowledge, 2020-and-up models are not showing these failings. Regardless, please take added precautions to operate your Sea-Doo within the prescribed guidelines outlined in your operator’s manual, as well as stay “on top” of your regular service schedule.

Additional photography and the video below via 3ft Deep.