Briggs & Stratton 44S977-0032-G1 Professional Series engine

Briggs & Stratton 44S977-0032-G1 Engine | 25 HP, 1-Inch Vertical Shaft

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Overview

Restore reliable power to your riding mower or zero-turn with the Briggs & Stratton 44S977-0032-G1 Professional Series engine. This seller-listed new engine delivers 25 gross HP from a 724cc V-twin and features a 1-inch diameter × 3-5/32-inch vertical crankshaft, electric start with ReadyStart, and a 16-amp charging system.

The 44S977 series is a widely used Professional Series platform for residential and light-commercial mowers. This specific 0032-G1 specification uses the common 1-inch shaft configuration that fits the majority of mid-size riding mowers and many zero-turns.

Confirm the complete engine specification before ordering. Match the full model-type-code number and physical shaft dimensions of your original engine. The 0032 and 0033 versions of this family use different shaft diameters and are not interchangeable.

Briggs & Stratton 44S977-0032-G1 Specifications

Manufacturer: Briggs & Stratton
Engine number: 44S977-0032-G1
Series: Professional Series
Power: 25 gross HP
Displacement: 724cc
Configuration: V-twin, overhead valve, vertical shaft
Crankshaft: 1-inch diameter × 3-5/32-inch length
Keyway: 1/4 inch
Crankshaft end: Drilled and tapped 7/16-20
Starting system: Electric start with ReadyStart
Charging system: 16 amp
Lubrication: Full-pressure lubrication with oil filter
Cylinder construction: Dura-Bore cast iron sleeves
Muffler: Typically not included (confirm with seller)
Condition: New, as listed by the seller

Shaft dimensions, charging system, and included components reflect the selected seller’s advertised configuration. Compare them with your original engine and confirm the complete code of the engine supplied.

Riding Mower and Zero-Turn Engine Fitment

This listing is organized around the 44S977-0032-G1 specification. A 25 HP Briggs Professional Series engine is a starting point for comparison, not automatic confirmation that this exact specification will fit.

Engine identification: Compare the full model, type, and code number stamped on your original engine.
Crankshaft: Confirm 1-inch diameter, usable length, keyway, and retaining-bolt thread. This is not a substitute for a 1-1/8-inch shaft application.
Mounting and clearance: Check mounting pattern, engine height, and clearance around the air cleaner, oil filter, and exhaust.
PTO clutch and drive pulley: Confirm shaft engagement, pulley position, and belt alignment. A 1-1/8-inch clutch bore will not fit this shaft.
Electrical system: Match starter connections, charging requirements, and safety-circuit wiring.
Controls: Confirm how the mower’s throttle and choke (or ReadyStart) arrangement works with this engine.

Common cross-references include earlier 44S877 and 44Q777 Professional Series engines with the 1-inch shaft. Always confirm the exact original specification with the seller before ordering.

What’s Included?

One engine in the seller’s advertised 44S977-0032-G1 configuration. Confirm whether a muffler, wiring harness, or installation hardware is included, and which components must be transferred from your existing engine.

Buy Through the Selected eBay Seller

Use the button to view the seller’s current price, stock, shipping options, and purchase terms. Payment, fulfillment, returns, and any warranty arrangements are handled through the seller’s offer. Price and availability may change.

Frequently Asked Questions

Is 44S977-0032-G1 the same as 44S977-0033-G1?

No. The 0032 version uses a 1-inch × 3-5/32-inch shaft. The 0033 version uses a 1-1/8-inch × 4-19/64-inch shaft. That difference affects the PTO clutch, drive pulley, and installation.

Can I select this engine by horsepower alone?

No. Use the original engine’s complete model and type number first. Horsepower, mower brand, and deck size alone do not establish compatibility.

Can I reuse my existing PTO clutch?

Only if its bore, mounting arrangement, and position match the 1-inch replacement shaft and your mower’s drive system.

Need help identifying your existing engine? Contact PTO Direct USA with clear photos of the engine model/type/code label and your mower identification tag.

Compare other options in our replacement engine collection, or browse our electric PTO clutch catalog.

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