The dry weight of Mercury 40HP FourStroke outboards ranges from 93 kg (204 lbs) to 118 kg (260 lbs), depending on cylinder layout, shaft length and equipped functions. Dry weight only counts solid motor parts without engine oil, gear fluid or fuel.
Three core assemblies make up its total mass. First, the powerhead is the heaviest part: lighter 3-cylinder blocks weigh far less than smooth-running 4-cylinder versions with extra valves, EFI systems and oil sumps. Second, the midsection and drive tube add weight—20-inch long-shaft models use longer reinforced aluminum housings than 15-inch short-shaft variants for taller boat transoms. Third, optional power trim & tilt units, electric starters and corrosion-resistant lower gearcases add extra mass.
Buyers check this weight to verify boat transom load limits, calculate shipping freight and judge if the motor can be lifted manually for transport or storage.
