Best Motor For Lawn Mower: Compare 10 Replacement Engines

#1 · Best Overall

1. Aceup Energy AE170V

• Dimensions: 12 x 11.8 x 9 in
• Weight: 18.1 lb

Best for: Primer-start walk-behind replacements.

Why it ranks #1: Its 4.4 HP, 173cc vertical-shaft design is explicitly for lawn mowers, with a specified 7/8-inch shaft and primer-assisted starting.

A red primer gives this 4.4 HP, 173cc vertical-shaft Aceup Energy engine a clear cold-start routine: press it three to five times before pulling the recoil starter. That setup suits a lawn-mower replacement where a manual start and compact engine are more relevant than electric starting or riding-mower power.

The 7/8-inch shaft is 3.16 inches long, with a 3/16-inch keyway and tapped 3/8-inch end, so those measurements provide concrete points for checking a mower’s drive connection. Its 0.9-gallon tank supports operation without an immediate refuel, while the recoil starter avoids reliance on an electric-start system. Metal cams, a forged crankshaft, and a cast-iron cylinder liner are specified construction features. For cold starts, use the primer sparingly; excessive pressing can flood the engine and make starting harder.

Skip it if you need electric starting or a riding-mower engine; this listing specifies recoil starting and 4.4 HP output.

Choose this Aceup Energy for a compatible lawn mower needing a 4.4 HP vertical-shaft engine and manual recoil start. Its shaft measurements are specific, so check the existing mower’s connection before treating it as a replacement.

Listed on Amazon as: Aceup Energy Gas Engine Vertical Shaft, 4.4HP 173cc 4-Stroke OHV Gas Motor with Primer for Lawn Mower, EPA Compliant

#2 · Best Push Mower

2. Briggs & Stratton 104M02-0197

• Dimensions: 16 x 16 x 16 in
• Weight: 22.5 lb

Best for: Fixed-speed push mower replacements.

Why it ranks #2: The listing specifies push-mower use only and gives a 7/8 x 3-5/32-inch keyed shaft, making its intended fit unusually clear.

A fixed 3100-rpm throttle and flywheel brake make the Briggs & Stratton 104M02-0197 specifically oriented to push mowers, rather than equipment that needs a different engine-control setup. Its 163cc vertical-shaft format offers a focused replacement choice when the mower’s design matches those requirements.

The keyed crankshaft measures 7/8 by 3-5/32 inches, giving buyers precise dimensions to compare with the existing push mower before installation. This engine’s flywheel brake must be released for the engine to function, a critical detail for setup and operation. Its throttle is fixed at 3100 rpm, rather than user-adjustable. Mounting holes are drilled only; the listing recommends nuts and bolts or self-tapping bolts from the existing equipment. The stated application excludes pressure washers, log splitters, and edgers.

Skip it if you need an engine for a riding mower, pressure washer, log splitter, or edger; this model is specified for push mowers only.

Choose this 163cc Briggs & Stratton for a push mower whose shaft and mounting arrangement match the listed dimensions. The fixed-speed throttle and flywheel-brake requirement make it a specialized replacement, not a general-purpose engine.

Listed on Amazon as: Briggs & Stratton 104M02-0197 7.25tp 163cc Vertical Shaft 7/8 x 3-5/32 Inch for mowers

#3 · Best 17.5 HP

3. Briggs & Stratton 31R977-0054

• Dimensions: 19 x 4 x 4 in
• Weight: 0.01 oz

Best for: Electric-start riding mower replacements.

Why it ranks #3: This 17.5 HP, 500cc vertical engine is identified as a common riding-mower replacement and includes electric start and a 9-amp system.

Electric-start-only operation is the defining choice on this 17.5 HP, 500cc Briggs & Stratton INTEK vertical engine, making it a candidate for compatible riding mowers already set up for electric starting. Its one-inch shaft and specified keyway provide useful connection details for a replacement check.

The shaft measures one inch by 3-5/32 inches, with a 7/16-inch tapped end and 1/4-inch keyway, so buyers can compare the crankshaft configuration with their mower before installation. A 9-amp electric-start system suits equipment configured for that arrangement, but there is no recoil-start option listed. The cast-iron cylinder sleeve and dual-element air filter are specified for extended engine life, while the patented linear balancing system is intended to provide smoother performance during mower operation.

Skip it if you need recoil starting or a push-mower engine; this INTEK is listed as an electric-start riding-mower replacement.

Choose this Briggs & Stratton for a riding mower needing a 17.5 HP vertical engine and electric start. Its shaft measurements and electric-only starting are decisive fit boundaries, so verify both against the existing setup.

Listed on Amazon as: Briggs and Stratton Vertical 17.5 HP 500cc INTEK Engine 9amp 1" x 3-5/32" #31R977-0054

#4 · Best V-Twin

4. Kawasaki FR730VJS00S

• Weight: 95 lb
• Material Type: Aluminum

Best for: High-output riding mower upgrades.

Why it ranks #4: Its 24 hp, 726cc OHV V-twin suits many riding mowers and zero-turns; the 1-inch shaft dimensions are specified for fit checking.

A 24 HP, 726cc OHV V-twin gives this Kawasaki vertical engine substantial output for a compatible riding mower or zero-turn replacement. Electric starting is included, while its precisely specified one-inch shaft helps buyers focus on a critical fit point before moving an existing mower to this engine.

The shaft measures one inch in diameter and 3-5/32 inches long, with a 7/16-inch threaded end and 1/4-inch keyway. Those details matter when matching the engine to the mower’s drive connection; Kawasaki offers other shaft sizes, so comparing the old crankshaft is especially important. The electric-start operation can suit a mower wired for that starting method. At 95 pounds, the engine also calls for a planned handling and installation process rather than casual lifting.

Skip it if you need a push-mower engine or cannot handle a 95-pound unit; this Kawasaki is a high-output riding-mower replacement.

This Kawasaki suits owners repowering a compatible riding mower or zero-turn who need 24 HP and electric starting. Make shaft dimensions and installation handling central to the decision, since the engine weighs 95 pounds.

Listed on Amazon as: 24hp Vertical 1"x3-5/32" Shaft, Fuel Pump, Electric Start, Kawasaki Engine

#5 · Best With Muffler

5. Briggs & Stratton 33S877-0043

• Dimensions: 5"D x 1"W x 3"H
• Weight: 56.9 lb
• Material Type: Cast Iron

Best for: 19 HP electric-start replacements.

Why it ranks #5: The 19 HP, 540cc vertical engine is a common riding-mower replacement and includes a muffler, electric start, and a specified 1-inch shaft.

A 19 HP, 540cc vertical engine with electric start and an included muffler makes the Briggs & Stratton 33S877-0043 a ready-to-consider riding-mower replacement package. Its one-inch shaft and defined keyway give buyers a concrete starting point for checking drivetrain compatibility.

The crankshaft measures one inch by 3-5/32 inches, with a 7/16-inch tapped end and 1/4-inch keyway, allowing a direct comparison with the mower’s existing connection. Electric start is specified as 9-amp, so the starting system is best suited to equipment configured for it. The included muffler removes one component from the separate-parts question, while the cast-iron cylinder sleeve and dual-element air filter are listed for extended engine life. Linear balancing is specified for smoother performance.

Skip it if you need recoil starting or a shaft other than the listed one-inch by 3-5/32-inch configuration.

Choose this Briggs & Stratton for a compatible riding mower needing 19 HP, electric start, and an included muffler. The shaft dimensions and electric-only starting are key boundaries to check against the existing equipment.

Listed on Amazon as: Briggs and Stratton Vertical Engine 19 HP 540cc 1" x 3-5/32" #33S877-0043

#6

6. Briggs & Stratton 33S877-0019-G1

• Weight: 77 lb
• Material Type: Iron

Best for: Electric-start riding mower repowers.

Why it ranks #6: This 19 HP, 540cc vertical engine is specifically listed for riding mowers and includes electric start, exhaust, and full-pressure lubrication.

A 19 HP, 540cc engine with electric start makes the Briggs & Stratton 33S877-0019-G1 a riding-mower replacement option for buyers who want push-button starting rather than a recoil pull. Its full-pressure lubrication and oil filter also give routine engine care a defined, serviceable system.

The 9-amp charging system accompanies electric starting, making this a fit for a riding mower whose setup uses those electrical functions. Full-pressure lubrication with an oil filter supports an oil-circulation and filtration arrangement, while the Dura-Bore cast-iron cylinder sleeve is specified for extended engine life. The OHV design is identified with cooler operation and long valve life. An exhaust is included, and the stated 3300 maximum RPM helps distinguish this engine’s operating specification when evaluating a replacement.

Skip it if you need a push-mower engine or a light, manual-start replacement; this is specified for riding mowers and weighs 77 pounds.

This Briggs & Stratton suits riding-mower owners replacing an engine who value electric starting, filtered full-pressure lubrication, and included exhaust. Confirm the mower’s mounting and connection requirements before choosing this 77-pound unit.

Listed on Amazon as: Briggs & Stratton 33S877-0019-G1 Professional Series 19 HP 540cc Vertical Engine

#7

7. Briggs & Stratton 31R907-0007-G1

• Dimensions: 48"W x 48"H
• Weight: 51 lb
• Material Type: Cast Iron

Best for: CARB-compliant 17.5 HP repowers.

Why it ranks #7: Its 17.5 gross HP, 500cc engine has electric start and a float carburetor, and the listing states that it is CARB compliant.

CARB compliance distinguishes this 17.5 gross HP, 500cc Briggs & Stratton engine for buyers whose repower choice must meet the listed emissions requirement. Its electric-start-only system and one-inch crankshaft dimensions make starting setup and mechanical compatibility central to deciding whether it suits a mower.

The crankshaft is specified as one inch by 3-5/32 inches and tapped 7/16-20, giving buyers measurable connection details for comparison with the existing engine. A 9-amp electric-start-only system suits equipment wired for electric starting, but does not offer a listed recoil alternative. The float carburetor is specified for consistent, easy starting, while the cast-iron cylinder sleeve and dual-element air filter are identified with extended engine life. Linear balancing is listed for smoother performance.

Skip it if you need recoil starting or a crankshaft other than the listed one-inch by 3-5/32-inch size.

This Briggs & Stratton suits buyers seeking a CARB-compliant 500cc repower with electric starting and a specified crankshaft. Check the shaft and electrical setup against the mower, especially if recoil starting is required.

Listed on Amazon as: Briggs & Stratton 31R907-0007-G1 500cc 17.5 Gross HP Engine with 1-Inch by 3-5/32-Inch Length Crankshaft Tapped 7-16-20-Inch

#8

8. Briggs & Stratton 44S977-0032-G1

• Dimensions: 19 x 16 x 18 in
• Weight: 83.8 lb

Best for: High-output mower repowers outside California.

Why it ranks #8: At 25 GHP, it has the highest stated power figure here and adds full-pressure lubrication and a 16-amp charging system; it is CARB non-compliant.

A 25 GHP vertical-shaft rating and 16-amp charging system make the Briggs & Stratton 44S977-0032-G1 a high-output repower option with substantial charging capacity specified. Full-pressure lubrication with an oil filter and a cast-iron cylinder sleeve add concrete maintenance and durability features for compatible equipment.

The full-pressure lubrication system includes oil filtration, giving the engine a defined lubrication arrangement for buyers comparing repower options. Its 16-amp charging system is a notable specification for a mower setup that uses engine charging capacity. The Dura-Bore cast-iron cylinder sleeve is listed for extended life, while the OHV design is associated with cooler operation and long valve life. However, this model is identified as CARB non-compliant and cannot ship to California, which directly limits where buyers can receive it.

Skip it if you need delivery in California; this Briggs & Stratton model is listed as CARB non-compliant and cannot ship there.

This 25 GHP Briggs & Stratton suits compatible equipment repowers where its charging and lubrication specifications fit the job. It is not an option for California delivery, so location is a firm boundary before evaluating fit.

Listed on Amazon as: Briggs & Stratton 44S977-0032-G1 25 GHP Vertical Shaft Engine, Black

#9

9. Briggs & Stratton 21R806-0047-F1

• Weight: 74.8 lb

Best for: EPA-compliant 344cc mower repowers.

Why it ranks #9: This 11.5 HP, 344cc vertical-shaft engine has an OHV design and cast-iron sleeve, but the listing stresses model-specific replacement fit.

EPA compliance and an 11.5 HP, 344cc vertical-shaft configuration define this Briggs & Stratton 21R806-0047-F1 for buyers seeking a replacement with a stated emissions-compliance feature. Its OHV design and cast-iron cylinder sleeve add specified operating and durability considerations to the repower decision.

The float carburetor is listed for consistent, easy starting, giving buyers a named starting-system feature to weigh when replacing an engine. Its OHV design is associated with cooler operation and longer valve life, while the Dura-Bore cast-iron cylinder sleeve is specified for extended engine life. The listing stresses that replacement engines are specific to the current model number, so checking the original engine identity is important before installation. EPA compliance is explicitly stated, and the engine’s listed weight is 74.8 pounds.

Skip it if you need an engine with listed shaft measurements before checking fit; this model stresses model-specific replacement matching and weighs 74.8 pounds.

This Briggs & Stratton is for owners considering an EPA-compliant 344cc engine for a carefully matched equipment repower. Check the original model number before proceeding, and plan for handling a 74.8-pound engine.

Listed on Amazon as: Briggs & Stratton 21R806-0047-F1 11.5 HP 344cc Vertical Shaft Engine

#10

10. Briggs & Stratton 13R232-0001-F1

• Dimensions: 48"W x 48"H
• Weight: 33 lb
• Material Type: Plastic

Best for: Maintenance-focused small-engine repowers.

Why it ranks #10: The listing describes a 33-pound OHV engine with a cast-iron sleeve but gives no vertical-shaft dimensions or mower-specific fitment, limiting confidence for this use.

A dual-clean air cleaner combines a pleated-paper filter with a foam pre-cleaner, giving the Briggs & Stratton 13R232-0001-F1 two specified filtration elements for engine protection. Its OHV design and Dura-Bore cast-iron sleeve further distinguish this small engine for owners prioritizing protective construction and valve-life features.

The dual-clean arrangement uses both a pleated-paper filter and a foam pre-cleaner, which the listing associates with maximum protection and extended engine life. A Dura-Bore cast-iron cylinder sleeve is also specified for extended life, while the OHV design is identified with cooler operation and longer valve life. Magnetron electronic ignition is listed for quick, dependable starts, and dual ball bearings are another named component. The supplied listing does not provide shaft dimensions or a specific mower application, so compatibility needs particular attention.

Skip it if you need a clearly specified mower replacement with known shaft measurements; this listing leaves those fit details unstated.

This Briggs & Stratton may suit buyers prioritizing filtration, cast-iron sleeve construction, and electronic ignition in a small-engine repower. The listing does not identify a mower application or shaft dimensions, making fit verification essential.

Listed on Amazon as: Briggs and Stratton 13R232-0001-F1 Engine,Black,14.5 x 12 x 13.5 inches