Skip to content
The Best Mowers

Research-led review · Updated May 2026

Cobra MX46SPB Review

By The Best Mowers UK · Research-led assessment from specs and verified owner reviews

Self-propelled petrol lawn mower on a UK lawn

Specs

Cutting width46 cm
EngineBriggs & Stratton 500E (140 cc)
DeckSteel
DriveVariable-speed self-propelled
Cut heights6 positions, 25-75 mm
Grass box55 litres
Cutting system4-in-1 (collect, mulch, side, rear)
Weight32 kg
StartRecoil with ReadyStart (no priming)
Warranty2 years

What owners praise

  • Briggs & Stratton engine - ReadyStart means no priming bulb, no choke fiddling. Pull and go, even after winter storage. The 500E is a proven unit with parts available everywhere.
  • Variable-speed drive - adjust your walking pace on the fly. Much better than single-speed rivals around corners and on slopes.
  • 4-in-1 versatility - collect, mulch, side-discharge, or rear-discharge. Most owners run mulch mode for routine cuts and switch to collection for the autumn leaf clean-up.
  • Build quality - steel deck, solid wheels, chunky bail lever. Feels like it'll last a decade with basic maintenance.

The drawbacks

  • Heavy at 32 kg - you won't be lifting this over garden steps easily. The self-propelled drive compensates on flat ground but steep banks require effort.
  • Cobra dealer network is thinner than Mountfield - fewer high-street service centres. Most servicing is through garden machinery specialists rather than B&Q or Homebase.
  • Price gap vs Mountfield - £120 more than the SP46 for a marginally better engine and variable-speed drive. Whether that's worth it depends on your priorities.
  • Fuel-sensitive like all modern petrol mowers - E10 goes stale in 30 days. Use stabiliser or Aspen 4T if it sits idle over winter.

How it compares

The budget alternative is the Mountfield SP46 at £329 - Italian engine, single-speed drive, £120 less. The premium step-up is the Honda HRX 476 VK at £999 - 20+ year lifespan, Xenoy deck, but more than double the price. The Cobra occupies the rational middle ground.

Who should buy it

UK lawn owners with 500-1,000 m² who want a proper engine without paying Honda prices. Buyers who value variable-speed drive for gardens with slopes or tight corners. Anyone who wants 4-in-1 flexibility without compromise.

Don't buy it if your lawn is under 400 m² (cordless is simpler and cheaper), if budget is your top priority (Mountfield SP46 at £329), or if you want a lifetime mower (Honda HRX at £999).

Frequently asked questions

Is the Cobra MX46SPB worth £449?+
Yes - the Briggs & Stratton 500E engine alone justifies the £120 premium over the Mountfield SP46. It's a proven American engine with a global parts network. The mower as a whole is a mid-range sweet spot: better engine than budget options, cheaper than Honda premium.
What engine does the Cobra MX46SPB use?+
Briggs & Stratton 500E Series - a 140 cc single-cylinder OHV four-stroke with ReadyStart (no priming, no choke). Widely regarded as one of the most reliable small engines available.
Cobra MX46SPB vs Mountfield SP46 - which is better?+
Cobra wins on engine pedigree (Briggs & Stratton vs Mountfield ST 140), variable-speed drive vs single-speed, and overall refinement. Mountfield wins on price (£329 vs £449) and similar real-world durability. If budget is tight, Mountfield; if you want the better engine and smoother drive, Cobra.
Does the Cobra MX46SPB mulch?+
Yes - it's a 4-in-1 system: collect, mulch, side discharge, and rear discharge. Mulching plug is included in the box.
How big a lawn can the MX46SPB handle?+
Comfortably 800-1,000 m². The self-propelled drive and 46 cm deck make it efficient on medium-to-large UK gardens. Above 1,000 m² you might prefer a wider 51 cm or 53 cm deck model.