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Briggs & Stratton 44S977-0033-G1 25 HP V-twin vertical-shaft replacement mower engine on a white background
  • Briggs & Stratton 44S977-0033-G1 25 HP V-twin vertical-shaft replacement mower engine on a white background
Briggs & Stratton 44S977-0033-G1 Engine — 25 HP, 1-1/8" Shaft

Briggs & Stratton 44S977-0033-G1 Engine — 25 HP, 1-1/8" Shaft

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Overview

The Briggs & Stratton 44S977-0033-G1 replacement engine is a 25 gross HP, 724cc Professional Series V-twin for select riding mower, lawn tractor and zero-turn repower applications. It features a vertical crankshaft measuring 1-1/8 inches in diameter × 4-19/64 inches long, electric start, ReadyStart and full-pressure lubrication.

Replacement references include 44S877-0001-G1 and 44Q777-3136-G5. Specific Husqvarna and Craftsman mower references are listed below to help identify the original engine and confirm the installation requirements.

Engine Specifications

  • Engine number: 44S977-0033-G1
  • Series: Briggs & Stratton Professional Series
  • Power: 25 gross HP
  • Displacement: 724cc
  • Configuration: V-twin, overhead valve, vertical shaft
  • Crankshaft: 1-1/8" diameter × 4-19/64" length
  • Keyway: 1/4"
  • Crankshaft end: Drilled and tapped 7/16"-20
  • Starting: Electric start with ReadyStart
  • Charging system: 16 amp
  • Fuel system: Gasoline with fuel pump
  • Lubrication: Full-pressure lubrication with oil filter
  • Cylinder construction: Dura-Bore cast iron sleeves

Replacement Engine References

Engine supplier cross-reference information lists 44S977-0033-G1 as a replacement for the following complete engine numbers:

  • 44S877-0001-G1
  • 44Q777-3136-G5
  • 44Q777-0136-G1
  • 44Q777-0006-G1
  • 44P777-0016-G1
  • 44P777-0016-E1

Match the complete engine model and type, including the suffix. Installation may require transferring mower-specific components or adapting controls and wiring.

Husqvarna and Craftsman Mower Application References

The following mower manuals identify original Briggs engines associated with this replacement family through engine parts catalogs. These are repower candidates requiring seller confirmation of the exact engine number and installation details.

Mower reference Original Briggs engine to match
Husqvarna GTH2448T, model 917.279260 445677-0476-E1
Husqvarna YTH2454, manual reference 287581 445677-0479-E1
Craftsman 917.276080, 48-inch garden tractor 446777-0244-E1
Craftsman 917.276081, 48-inch garden tractor 446777-0244-E1

Match the engine currently installed. Mower names can cover different engines and production versions, and older equipment may already have been repowered. Send the seller your engine label and mower identification tag before ordering.

Installation Details to Confirm

  • Shaft and PTO fit: Compare shaft diameter, length, keyway, retaining-bolt thread, clutch position and pulley alignment.
  • Mounting and clearance: Check the engine mounting pattern and clearance around the hood, air cleaner, oil filter and exhaust.
  • Electrical system: Confirm the starter, charging connection, fuel-solenoid connection and ignition shutdown wiring match the mower. Some earlier replacement instructions call for transferring a six-pin harness.
  • Controls: Confirm how the mower's throttle controls work with this ReadyStart engine and whether the original manual choke control is needed.
  • Exhaust and supplied parts: Ask which muffler, exhaust hardware and installation components are included. Original mower-specific exhaust parts may need to be reused or replaced.

Frequently Asked Questions

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

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

Can I select this engine by horsepower alone?

Use the original engine's complete model and type number first. Horsepower, mower brand and deck size alone do not establish compatibility.

Is this a complete mower conversion kit?

This listing is for a replacement engine. Check the eBay seller's description for the included components and any additional parts required for your mower.

Parts Help From PTO Direct USA

Text a Photo. Get Parts Help.

Text your engine model, type and code label and your mower's model and serial tag to 541-361-8778. Include photos of the crankshaft, PTO clutch, wiring connectors and exhaust arrangement.

Open the Parts Desk

Fitment support before and after purchase. Final engine compatibility and included installation parts should be confirmed with the selling dealer.

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

Affiliate disclosure: This engine is sold and fulfilled by an independent seller on eBay. PTO Direct USA may earn a commission if you buy through the affiliate link. Check the seller listing for current price, availability, shipping, returns and warranty terms.

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