Multiquip 21639 Yanmar 55HP 4TNV84T-DSA Engine

The Multiquip 21639 Yanmar 55HP 4TNV84T-DSA Engine is a genuine OEM power unit designed for STX55J6 and STX55Y6 super-sized hydrostatic ride-on power trowels. As a direct Multiquip OEM component, part 21639 is built to the exact output and dimensional specifications required by these machines — no compromise on fit or performance. This engine is confirmed compatible with the STX55 series, making it the correct choice when a full engine replacement is needed to restore full operating capability.

Key Features

• Genuine OEM Power Output: — The Yanmar 4TNV84T-DSA is rated at 55HP and matched precisely to the hydraulic load demands of the STX55 hydrostatic drive system, ensuring the trowel delivers full blade speed and drive response.
• Direct Engine Swap Compatibility: — Engineered to the original mounting, shaft, and connection specifications of the STX55 platform, allowing a straightforward replacement without custom fabrication or adapter work.
• STX55 Series Fitment: — Confirmed for use on STX55J6 and STX55Y6 super-sized hydrostatic ride-on trowels.
• Hydrostatic System Integrity: — A correctly rated engine maintains proper hydraulic pressure across blade pitch control and ground drive circuits — an underpowered or mismatched engine causes sluggish blade response and drive instability on large finishing passes.
• Verified OEM Part Number: — Sourced directly through Multiquip's authorized parts network; part number 21639 matches the original build specification for these trowel models.

The engine is the primary power source for the STX55 hydrostatic ride-on trowel, driving the hydraulic system that controls both blade pitch adjustment and machine propulsion. On a hydrostatic trowel of this size, consistent engine output is critical — any loss of power directly affects the hydraulic pressure available to maintain blade angle and ground speed during finishing operations. When the engine fails or reaches end of service life, replacing it with the correct OEM unit, such as the Multiquip 21639 Yanmar 4TNV84T-DSA, ensures the hydraulic circuits operate within their designed pressure range and the machine performs as intended.

Part Details

Compatibility & Fitment

Verify Before You Order

Fitment is machine-number and revision-specific; always confirm your model and serial number against the fitment list.

Why Buy From DHS Equipment

Every part is verified against the manufacturer's part number before it ships, so what you order is what arrives. We carry parts from leading OEM brands and our own DHS Quality Parts line of professional aftermarket components. Need help finding the right part? Our team is available to confirm compatibility whenever you need it. Orders are processed fast to keep your jobs on track. We don't just sell parts. We keep you jobsite ready.

Questions? Contact our team at [email protected] or 866-611-9369 — DHS Equipment is here to help you maintain peak performance.