Rebuilding the Engine of a Yamaha FX SVHO

Aug 24, 2023

Last year around this time, we started a major project: fixing up a 2014 Yamaha FX SVHO. We documented this entire tear-down and reassembly in the second season of our Project X video series (and if you haven't watched it yet, you should). I had the opportunity to help out on this rebuild, and I thought now would be a good time to reflect on what all went into this project.

Now I’m no stranger to personal watercraft (PWC), but I had never worked on anything quite this big before. I grew up mostly working on 650cc two-cylinder Kawasaki Jet Skis, of which my father and I owned quite a few. They were slow and unreliable but cheap to buy and maintain. I had learned quite a bit working on those smaller jet skis over the years, but I’d soon find out that Project X had a few surprises in store for me.

I came to MPN after Season 1 (where the team tackled a 2007 Polaris Sportsman 800 ATV) had wrapped up, though I did have an opportunity to ride the 800 Sportsman for a bit. When I found out that Season 2 would involve a PWC, I was very excited, and I knew I wanted to be involved in the project! The PWC was already selected, so we set out to plan exactly what work we would try to accomplish in our relatively short timeline. It was a tall task, but we had a talented team of professionals, and we were confident that we could make it happen.

Episodes 1 and 2 were filmed without a hitch. We introduced the FX SVHO and the owners Dean and Jed, and then we talked a bit about what we were going to try and achieve with the project. "Big Blue," as we affectionately called it, was a powerful machine, but it was in need of some mechanical rehab. The paint finish showed plenty of dings, blemishes and scratches, but to us that just meant that it was being used. The speedometer wasn't working at the time, and Dean and Jed had noticed some oil was burning. So, we knew what we needed to keep an eye out for once we started working on the engine.

In Episode 3, our own Joe Keene, automotive content video producer, started out by removing the engine from Big Blue, which I can tell you was no small task. It took a ton of effort to get that engine to come out, and I tip my hat to Joe! Once the engine was on the work bench, he started working on disassembling it. Using a factory service manual—which was about as clear as mud to read (think terribly Chinese translated text)—we ran into our first snag. Trying to remove the drive coupler from the back of the engine proved to be too much for one person to do alone, so Eric Garbe, our senior automotive technical writer, and I came in to lend a few extra hands. With a bit more manpower, we were able to get the engine torn down the rest of the way, and we were ready to shift our focus back onto the hull.

Episode 4 is all about the trim and steering cables. These cables are maintenance-free, but they’ll still need to be replaced from time to time. They can be a real challenge when it comes to sneaking them out with the engine still in place, but since ours was already removed, this proved to be a pretty easy task. We talked about how to replace both cables, install the new ones, and how to adjust them so they work perfectly. As an added bonus, I discovered that the speedometer pickup had been sheared off, which definitely explains why the speedometer wasn't working! We added that to the list of parts we needed to replace and kept moving forward.

Eric and Joe filmed Episode 5 together while reassembling the rotating assembly. The crankshaft, connecting rods and pistons were all replaced and measured, and then everything was torqued down in accordance with the service information. That was a really, really long day of shooting for those guys. There was a ton of work that went into this episode!

I took the reins for Episode 6 and spent the next few days removing the jet pump and replacing the impeller. Let me tell you, I was unprepared for how much of a fight this job would be. Just getting the jet pump out of the hull was a challenge, but then I needed to loosen the impeller and remove it from the driveshaft. This proved to be way more than what I could accomplish alone, so we reached out to a nearby shop to lend a hand. With the old impeller removed, I went ahead and rebuilt the bearings and seals inside the jet pump housing. I ended up needing to improvise some tooling and creative solutions to get it done, but it all went relatively smoothly. Then I wrapped up the episode by installing the new cast aluminum impeller that SBT had sent over to us.

Joe took over for Episode 7 and worked through rebuilding the cylinder head. This included removing the valve springs and valves, inspecting all of the components and replacing them. He then wrapped up the episode by installing the cylinder head onto the engine block and torquing everything to specification.

I came back in front of the camera for Episode 8, where I rebuilt the intermediate housing and driveshaft. This is the small driveshaft that connects between the rear coupler on the engine and the impeller. There are a few bearings and seals inside of this aluminum housing, and again, I had no idea how challenging it would be. But with some improvised tools and creativity, we got the drivetrain work all wrapped up.

Episode 9 features Joe installing the camshafts and setting base timing on the engine. I reassemble the jet pump in Episode 10, and I changed over to a stainless steel aftermarket impeller. Now it was time to start putting Big Blue back together again! Joe took over for Episode 11 and worked his tail off to get the freshly rebuilt engine back into the hull. Then in Episode 12, we see Big Blue get some cosmetic upgrades. We stripped off the old, beat-up mats; removed all of the decals; and wrapped the entire hull with an eye-popping orange! New mats and a banging sound system came next, and then the transformation was complete.

Episode 13 was bittersweet to film. We gave the jet ski back to Dean and Jed, and we got to record their reaction to seeing the finished product. This entire project was such a great experience for all of us, and I can't wait to do it all again sometime in the future!

Looking back on this project, I can say I definitely learned a few things. Much of my past experience with PWC was with much smaller, far less powerful two-cylinder machines. We’re only talking about engines with 40 to 50 horsepower, which is a far cry from the 300 horsepower that the FX SVHO makes. As a result, everything on the FX SVHO was bigger, beefier, stronger and tighter. This, of course, makes a lot of sense. The driveline would need to be beefier in order to handle that sort of power.

I noticed another striking difference while working on Big Blue: It seemed like every single nut, bolt and fastener had thread locking compound on it. I suppose this is also to be expected, given how much power the engine makes. With all of that power comes noise, vibration and harshness (NVH), not to mention the increased speeds the FX SVHO is capable of reaching. Fasteners will be subjected to extreme stress, and they need to remain tight and hold the various components in place at all times. Whether it was thread locking compound or thread sealing compound, I found myself needing to really take my time whenever I was removing fasteners, especially in the area of the jet pump. Better to take my time and be careful to avoid stripping or pulling threads out of an aluminum housing!

So, what sort of machine should we work on next time? Let us know — we’d love to hear what you want to see!