Honda HRG466 vs Mountfield SP46 for Mowing a Wet 300-Square-Metre Lawn

Wet grass is where the HRG466 and the SP46 stop being interchangeable. On a bone-dry lawn either machine cuts the 300m2 cleanly and neither owner would notice much. Push into grass still holding overnight rain and the differences in deck volume, blade twist and discharge angle turn into the difference between a continuous cut and a stalled chute packed with clippings.

The chute is the first thing that fails

Run the Mountfield SP46 into wet 4cm growth on the second-lowest of its seven cutting heights and the standard side-and-rear collection path starts backing up within a few metres. The SP46 uses a pressed-steel deck with a relatively shallow throat feeding the grass box, and saturated clippings compact against the deck wall instead of being thrown clear. The symptom is familiar to anyone who has mowed after rain: the box stops filling, a wet plug forms at the deck outlet, and cut quality collapses because clippings recirculate under the blade instead of exiting.

The Honda HRG466 handles the same conditions differently because of its twin-blade Micro Cut arrangement on the higher-spec variants, and a deeper polymer deck on the standard HRG466. The upper blade re-cuts material the lower blade has already lifted, which reduces clipping length before it reaches the outlet. Shorter clippings pack less readily. In practice the Honda tolerates one or two more passes in wet grass before it demands a chute clearance, which on a 300m2 plot is the margin between finishing uninterrupted and stopping twice.

Neither machine escapes physics entirely. Wet mowing means more frequent underside cleaning on both, and both benefit from raising the cut by one notch when the grass is heavy.

Engine and drive under load

The HRG466 runs Honda’s GCV170 overhead-cam engine at 166cc, while the SP46 in current specification carries a Mountfield-branded engine, historically the 123cc to 150cc range depending on model year and market. That displacement gap matters most in wet grass, where blade drag rises sharply. The larger Honda unit holds blade speed under load, and blade speed is what actually cuts. When engine revs sag on a heavily loaded deck, the blade tears rather than slices and the lawn shows ragged brown tips two days later.

Both machines are self-propelled through the rear wheels. The SP46 uses a single-speed drive engaged by a bail lever, simple and cheap to service. The HRG466 offers variable Smart Drive on several trim levels, letting the operator dial ground speed down when the deck is working hard in wet growth. On soft ground that variable control is genuinely useful: matching forward speed to how fast the deck can actually process saturated grass prevents the overload that clogs the chute in the first place.

Rear-wheel traction on both suffers on a wet slope. Neither is a hillside specialist. On the flat-to-gentle 300m2 lawn most owners are describing, traction is adequate for both, though the Honda’s higher kerb weight gives marginally better grip when the tyres are cutting into soft turf.

One point on noise

The GCV170 on the Honda idles and cuts noticeably quieter than the older Mountfield engine at comparable throttle. For gardens hemmed in by neighbours, that single difference decides more purchases than cut quality does.

Blade condition changes everything in the wet

A dull blade is tolerable on dry grass and unusable on wet. On dry growth a blunt edge still fractures the leaf; wet blades of grass fold away from a dull edge and spring back uncut, so a worn blade on either the HRG466 or the SP46 produces a visibly striped, half-cut finish after rain. The wet-lawn test is the honest test of blade sharpness.

Sharpening either blade follows the same routine. Disconnect the spark plug lead first, tip the machine with the air filter and carburettor uppermost to avoid oil flooding the cylinder, and mark the blade orientation before removal. Both use a single central bolt, though the Honda’s twin-blade Micro Cut assembly stacks two blades and a boss that must go back in the correct sequence. A flat mill file or a diamond file restores the factory bevel, roughly 30 degrees, working only on the top face of the cutting edge and keeping the file strokes even along both wings.

Balance is the step most owners skip and the one that shortens engine bearings. After filing, hang the blade on a nail through the centre hole. If one wing drops, file metal off the heavy side, not the edge, until it hangs level. An out-of-balance blade at 3,000 rpm sends vibration straight into the crankshaft. The same diamond file that restores a mower blade also works on secateur blades and hoe edges, so the tool earns its place in the shed beyond one job.

Collection versus mulching on saturated grass

Mulching wet grass is a losing proposition on both machines, and the reason is the same clumping that clogs the chute. The HRG466 accepts a mulch plug and its twin-blade design mulches respectably in dry conditions, producing fine clippings that vanish into the sward. Introduce moisture and those clippings mat into clumps that smother the lawn and invite fungal problems within days. The SP46 with its mulch kit fares worse still, since the shallower deck gives clippings less time to be chopped before they settle.

For the wet 300m2 scenario, collection is the working choice on both machines, accepting that the box fills faster with heavy wet clippings and needs emptying more often. The SP46’s grass box runs to around 60 litres depending on model, the HRG466 to a similar 55 to 60 litres. Wet clippings are dense, so the practical fill point arrives well before the volumetric limit. Expect to empty three to four times across 300m2 in genuinely wet grass on either machine, roughly double the dry-grass frequency.

There is a case for leaving wet grass entirely and waiting for it to dry, but owners rarely have that luxury when growth is racing in spring. Given the constraint of mowing wet, the deeper Honda deck and its re-cutting blades keep collection flowing longer between clearances.

Servicing cost over a decade

Over ten years the servicing gap between these two is real. Honda dealer parts and the GCV170’s overhead-cam design cost more up front, but the engine’s reputation for 500-plus hours before major attention is well earned. The Mountfield engine and drive are cheaper to buy parts for and simpler to service at home, which suits an owner who does their own maintenance and accepts replacing consumables more often.

A worked comparison: budget an annual service of oil, air filter and blade sharpen. On the SP46, home-serviced, that runs roughly 15 to 25 pounds a year in parts. On the HRG466, genuine Honda oil and filter push the figure to around 25 to 35 pounds, with the twin-blade set costing more to replace than the Mountfield’s single blade when the time comes. Across a decade the Honda costs perhaps 100 to 150 pounds more to keep running, set against a machine that typically holds resale value better and starts more reliably from cold.

The drive system is where the SP46 claws back ground. Its single-speed transmission has fewer parts to fail than the Honda’s variable Smart Drive, and the belt and cable are inexpensive when they eventually stretch or snap. An owner who values a machine they can strip and fix with basic tools may weigh that simplicity above the Honda’s engine longevity.

Which finishes the wet lawn cleaner

On the specific job, a wet 300m2 lawn cut with collection, the HRG466 finishes with fewer stops and a cleaner cut because its deeper deck and twin blades resist the clogging that stalls the SP46. The Mountfield remains the stronger value proposition for a dry lawn and a hands-on owner, where its lower running cost and serviceable drive matter more than wet-weather deck volume.

What neither specification sheet answers is how each deck behaves after five years of wet mowing, once grass residue has scoured the polymer or corroded the steel at the outlet lip. That accumulated wear may narrow the clogging gap more than any figure printed at purchase.