{
  "type": "product",
  "id": "hirth-engines-3503",
  "url": "https://www.nomyparts.com/companies/hirth-engines/products/3503/",
  "name": "3503",
  "fullName": "3503 liquid-cooled two-stroke inline aircraft engine",
  "manufacturer": {
    "id": "hirth-engines",
    "name": "Hirth Engines",
    "url": "https://www.nomyparts.com/companies/hirth-engines/"
  },
  "category": {
    "id": "propulsion",
    "name": "Propulsion"
  },
  "subcategory": {
    "id": "combustion-engines",
    "name": "Combustion engines"
  },
  "description": "The Hirth 3503 is a liquid-cooled, twin-cylinder two-stroke piston engine for light aircraft and rotorcraft. Its 51.67 kW measured output and 625 cm³ displacement support propeller-driven installations, with an optional reduction gearbox.",
  "manufacturerPage": "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
  "certifications": [],
  "specifications": [
    {
      "id": "grade",
      "name": "Grade",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": "Professional"
    },
    {
      "id": "market",
      "name": "Market",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": "Civil"
    },
    {
      "id": "platform-class",
      "name": "Platform class",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": [
        "Manned aircraft"
      ]
    },
    {
      "id": "airframe",
      "name": "Airframe",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": [
        "Fixed-wing",
        "Helicopter"
      ]
    },
    {
      "id": "availability",
      "name": "Availability",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": "In production"
    },
    {
      "id": "mass",
      "name": "Mass",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": 33.5,
      "unit": "kg"
    },
    {
      "id": "dimensions",
      "name": "Dimensions (L × W × H, mm)",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": "456 × 396 × 411 mm"
    },
    {
      "id": "max-power",
      "name": "Max power",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": 51.67,
      "unit": "kW",
      "si": {
        "value": 51670,
        "unit": "W"
      }
    },
    {
      "id": "engine-type",
      "name": "Engine type",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": "2-stroke"
    },
    {
      "id": "displacement",
      "name": "Displacement",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": 625,
      "unit": "cc",
      "si": {
        "value": 0.000625,
        "unit": "m³"
      }
    },
    {
      "id": "fuel-type",
      "name": "Fuel type",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": "Gasoline"
    },
    {
      "id": "specific-fuel-consumption",
      "name": "Specific fuel consumption",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": 436.43,
      "unit": "g/kWh"
    },
    {
      "id": "max-speed",
      "name": "Max speed",
      "sources": [
        "https://hirthengines.com/wp-content/uploads/2025-3503.pdf"
      ],
      "verified": "2026-11-08",
      "value": 6500,
      "unit": "rpm"
    },
    {
      "id": "cylinders-rotors",
      "name": "Cylinders / rotors",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": "Two inline cylinders"
    },
    {
      "id": "cooling",
      "name": "Cooling",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": "Liquid"
    },
    {
      "id": "tbo",
      "name": "TBO",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": 1000,
      "unit": "h",
      "si": {
        "value": 3600000,
        "unit": "s"
      }
    },
    {
      "id": "starter",
      "name": "Starter",
      "sources": [
        "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
        "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/"
      ],
      "verified": "2026-10-19",
      "value": "Electric starter (3503E specification)"
    }
  ],
  "sources": [
    {
      "url": "https://hirthengines.com/3503-liquid-cooled-70hp-two-stroke-engine/",
      "checked": "2026-10-25"
    },
    {
      "url": "https://hirthengines.com/two-stroke-engines-for-uav-ultralight-applications-hirth-engines/",
      "checked": "2026-10-25"
    },
    {
      "url": "https://hirthengines.com/wp-content/uploads/2025-3503.pdf",
      "checked": "2026-11-08"
    }
  ],
  "updated": "2026-11-12",
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "licenseName": "CC BY 4.0",
  "attribution": "Source: NomyParts, https://www.nomyparts.com/companies/hirth-engines/products/3503/"
}