How does a 3 cylinder Rotex engine seem to outperform a 4 cylinder Yamaha engine?

[dwakeman]

So I’ve been wondering, how does a three cylinder Rotex ACE 1630 engine produce 325 HP when the four-cylinder 1.8L SVHO Yamaha engine only produces 250HP? The Yamaha has peak torque of 148 Lb-ft. I was hoping to find torque numbers the Rotex engine, but was not able to. It also seems that the Rotex engine is a bit more fuel efficient. Is the Rotex engine just better engineered than the Yamaha engine, or am I missing something?

 

[biffdotorg]

That's an age old debate between brands. And the common consensus was that BRP wrings every hp out of their engines as possible to win the hp race. Where as Yamaha will tune theirs for reliability and leave a pile of hp on the table. Letting the aftermarket do what they do best.

Go follow the guys on Greenhulk and see how much more hp they can get out of a GP1800r with SVHO than any Rotax engine. It is the engine of choice for big power mods.

Yamaha has always powered their boats to give very acceptable performance for the capacity of each hull design, but keep the engines super reliable. You will hear of very few folks complain of engine issues in comparison to the amount of boats sold. Sure there are plenty of mfgs pushing out similar sized boats that are faster, but these hulls were not designed to push past the speeds they are at now comfortably.

Yamaha also realized the need for a bit more hp after the first couple years of the 25' hull. And responded with the 1.9ltr engines. Again, providing adequate hp without compromising reliability or replacing the entire pump system.

Yamaha has done the same in all their other powersport lines. The YXZ SXS and Arctic Cat Wildcat XX have a derivative of the TR1 that pushes 135hp without turbo. Aftermarket guys can push that engine past 300hp on pump gas. The Sidewinder in the sled line also has a similar turbo triple pushing 204hp on pump gas reliability while the aftermarket guys have pushed that engine past 350hp. The engine in my Yamaha Apex is a sub 1000cc NA engine pushing out 165hp. Many have pushed that engine past 400hp with a turbo and put them in SXS. I feel 165 is plenty in my trail tank.

And these two examples are done with 998cc triples. Need will never come into the conversation when talking hp. But at 204hp, that Sidewinder is way over the top when it comes to sled hp. And for a trail runner, the YXZ at 135, and the Arctic Cat Wildcat xx with the same engine are trail weapons.

The biggest indication of reliability is what do the PWC rental shops have and your question will be answered.

 

[dwakeman]

That's an age old debate between brands. And the common consensus was that BRP wrings every hp out of their engines as possible to win the hp race. Where as Yamaha will tune theirs for reliability and leave a pile of hp on the table. Letting the aftermarket do what they do best.

Go follow the guys on Greenhulk and see how much more hp they can get out of a GP1800r with SVHO than any Rotax engine. It is the engine of choice for big power mods.

Yamaha has always powered their boats to give very acceptable performance for the capacity of each hull design, but keep the engines super reliable. You will hear of very few folks complain of engine issues in comparison to the amount of boats sold. Sure there are plenty of mfgs pushing out similar sized boats that are faster, but these hulls were not designed to push past the speeds they are at now comfortably.

Yamaha also realized the need for a bit more hp after the first couple years of the 25' hull. And responded with the 1.9ltr engines. Again, providing adequate hp without compromising reliability or replacing the entire pump system.

Yamaha has done the same in all their other powersport lines. The YXZ SXS and Arctic Cat Wildcat XX have a derivative of the TR1 that pushes 135hp without turbo. Aftermarket guys can push that engine past 300hp on pump gas. The Sidewinder in the sled line also has a similar turbo triple pushing 204hp on pump gas reliability while the aftermarket guys have pushed that engine past 350hp. The engine in my Yamaha Apex is a sub 1000cc NA engine pushing out 165hp. Many have pushed that engine past 400hp with a turbo and put them in SXS. I feel 165 is plenty in my trail tank.

And these two examples are done with 998cc triples. Need will never come into the conversation when talking hp. But at 204hp, that Sidewinder is way over the top when it comes to sled hp. And for a trail runner, the YXZ at 135, and the Arctic Cat Wildcat xx with the same engine are trail weapons.

The biggest indication of reliability is what do the PWC rental shops have and your question will be answered.

Thank you @biffdotorg for this very thorough answer. It’s good to know that the Yamaha engines have much more capability and our responsibly tuned for typical use.

I sure hope that someone buys Arctic Cat soon and brings the brand back as I love their machines. My first snowmobile was a Cat.