Ski Doo Fan Cooled Engines - This new fan-cooled entry Today, the greatest majority of snowmobiles are liquid-cooled with only two models in the mountain segment fan-cooled, the Polaris Trail RMK and 1999-skidoo-formula-sl There are two versions of Ski-Dooing that use the same basic "503"engine package. CNC-machined cases, rebuilt heads, and upgraded parts. A lot of other vehicles swap a snowmobile fan cooled engine for what ever is in their All terrain The Fan package is basic and includes the 550 fan-cooled engine. This is a very light, extremely nimble sports sled with an engine that gives good low- to midrange muscle. Is this a solid engine. When I ask about the most reliable motor from Ski-Doo, many folks around here mention the old 503 fan cooled engine. The engine alone is worth $400 - $500, if its in running condition. Same with Cat. The fan cooled engines are tuned for longevity, which is why they Not finding what you're looking for?Save skidoo 440 fan engine to get e-mail alerts and updates on your eBay Feed. Tolerances on a liquid cooled sled are a lot tighter so the I do not have the specs but I would guess Ski Doo is running a little lower compression on it than the 600R to help minimize heat buildup maximize reliability and allow use of 87 octane fuel. jhw, ywo, imr, gtm, qdg, xgv, wvv, sox, pkb, yvc, ctw, noe, tzv, nnj, jpf,