I'm curious. If 12-15 model years were the same design, why are the 14 and 15 models "anecdotally" more likely to fail than say a 12 or 13 model year? i'm a seadoo guy and have no dog in this fight, but like others, have read the posts when they come up and am wondering if someone has a rational hypothesis.....
That's a good question, and I am glad you asked. Trust me, this is just a hypothesis as it held true for the Yamaha line of SXS and Snowmobiles that standardized on the 1049 Triple Four stroke. And the newer version, the 998 Triple Four stroke.
When Yamaha started turbo charging that engine, they had to play with the internals to beef them up for boost. They also needed to standardize on a number of components, to cut costs and make the boosted engine share as many of these parts (minus the turbo and plumbing) without raising the cost of the non-boosted engine too much.
So what do you get, you get one with upgraded internals for boost, and one with 3/4 of the upgraded internals, and possibly some made a bit cheaper. But still providing the same performance as the previous years.
That being said, we had NA 1.8ltr engines since 2010, and the SC 1.8 in the 192, as well as comparable waverunner models. When they wanted to go into mass production of the intercooled SVHO, yet again, more upgragraded shared components and possibly some cheapened. This does take time, so it didn't quite line up with the release of the SVHO in the Waverunner, 195 and 275 models. But the damage was done and we had a short run of potential problems.
I don't think QC caught it as the numbers were just not there to support an issue. And that is why Yamaha kept it as a TSB, knowing that timing chain issues have happened in other model years, as it's a moving part like any other. But not in any quantity till the end of 2014/early 2015. And still not to the point of the recall. Late 2015, they rectified the problem and all is good. But yet it still freaks a few folks out with later model post 2015 units, as a timing chain will fail once in a great while. So those few question whether it was upgraded or not. It was.
This happened in the Yamaha snowmobile line as well, but folks were boosting non turbo Yamaha models in roughly the same model years, not realizing Yamaha had switched some cranks that were not as ready for boost as previous years. This was quickly rectified. But Yamaha had it a bit easier, as they had yet to release an OEM Turbo, so they could have easily placed the blame on third party turbo's. They didn't and took care of the customers on that too. As we know, they released their 208hp 998 triple in 2017, and it has been an amazing power plant since. Folks have been pushing that motor beyond double that hp. So try not to giggle when someone says they don't push their stock yamaha very hard, when there are other Yamahas taking way more abuse than we can dish out in this format.