Snowmobile Powertrains
Five Engines. One Obsession.
From the efficient 650 Patriot to the turbocharged Patriot Boost and the smooth 4-stroke ProStar S4 — here's how each Polaris engine rides, and which sleds you'll find it in.
2-Stroke vs. 4-Stroke — the quick version
2-Stroke
Lightweight and explosive — fires every revolution for instant throttle response and a huge power-to-weight punch. The choice for aggressive trail, deep-snow and performance riders. (650, 850, Patriot 9R and Patriot Boost.)
4-Stroke
Smooth, quiet and efficient — sips fuel and shrugs off long miles with low maintenance. Ideal for touring, 2-up and utility riders who want to ride all day. (ProStar S4.)
650 Patriot
Built on the proven 850 architecture, the 650 Patriot delivers smooth power, quick response and standout efficiency — up to 40% less fuel and 10% less oil than the previous 600. A brilliant everyday trail and crossover engine.
850 Patriot
The heart of the Patriot family. Refined over 25+ years of Liberty engine heritage, the 850 delivers punchy acceleration, razor-sharp response and legendary durability — the benchmark all-around 2-stroke.
Patriot 9R
The big-bore member of the Factory Mod family — and the most powerful naturally-aspirated engine Polaris has ever built. Race-focused porting and lightweight internals deliver about 7% more horsepower and up to 12% more torque than the 850.
Patriot Boost
The turbocharged heart of the Factory Mod family — and the most powerful engine Polaris builds. A patented water-cooled vertical turbo delivers up to 9 PSI of boost: about 10% more power at sea level and up to 50% more at 10,000 ft versus the 850.
ProStar S4
Based on the proven ProStar architecture from millions of Polaris off-road vehicles, the S4 4-stroke is smooth, quiet and remarkably efficient. Eco, Standard and Sport drive modes make it as easy-going or spirited as you like — the go-anywhere touring and utility engine.
At a Glance
| Engine | Type | Displacement | Bore x Stroke | Cooling | Best For |
|---|---|---|---|---|---|
| 650 Patriot | 2-Stroke | 649 cc · 2-cylinder | Smaller bore · 74 mm stroke | Liquid-cooled | Efficient, smooth all-around trail riding |
| 850 Patriot | 2-Stroke | 840 cc · 2-cylinder | 85 x 74 mm | Liquid-cooled | Benchmark performance & durability |
| Patriot 9R | 2-Stroke · Factory Mod | 899 cc · 2-cylinder (88 x 74 mm) | 88 x 74 mm | Liquid-cooled | Maximum naturally-aspirated performance |
| Patriot Boost | Turbo 2-Stroke | 840 cc · 2-cylinder, turbocharged | 85 x 74 mm | Liquid-cooled (water-cooled turbo) | Ultimate power at any elevation |
| ProStar S4 | 4-Stroke | 998 cc · 2-cylinder (93 x 73.5 mm) | 93 x 73.5 mm | Liquid-cooled | Long-range touring & low-maintenance miles |
Not sure which engine is right for you?
Compare sleds side by side, or talk to our team — we ride these all winter and we'll help you dial in the perfect setup.