Why Does a Lawn Mower Shut Off in Wet Grass?

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Lawn Mower Shut Off

Mowing the lawn is a regular chore for many homeowners. However, when the grass is wet from rain or morning dew, you may find that your lawn mower suddenly shuts off while in use. This can be frustrating and leave you with an unfinished lawn. But why does wet grass cause a lawn mower to shut off?

Wet grass can cause a number of issues that may lead to your mower shutting down. When the blades of grass are wet, it affects the cutting efficiency and operation of the mower in various ways. So understanding the impact of mowing wet grass and the potential damage it can cause to your lawn mower will help you decide whether to wait until the lawn dries out before mowing.

In this article, we’ll look at the key reasons why a lawn mower shut off when going over wet grass. We’ll also provide tips on safely mowing damp grass if needed and discuss how different mower types, like electric and push mowers, handle wet lawn conditions.

Why Does My Lawn Mower Shut Off in Wet Grass?

Your Lawn mower shuts off in wet grass because wet grass creates a higher resistance, which makes it tougher for the blades to spin. This resistance overloads the engine, causing it to shut off as a safety measure.

7 Reasons Not to Mow in Wet Grass

1. Clogged Mower Deck

Clogging is one of the biggest reasons lawn mowers shut down when mowing wet grass. As the blades cut through wet grass, the moisture makes the clippings stick together as the chute gets clogged up with thick wet clumps.

This clogging stops proper discharge of grass clippings from under the deck. The accumulated clumps under the mower deck force the blades to slow down and eventually seize up. This excessive obstruction will cause the mower motor to shut off automatically.

Clogging issues are most noticeable when mowing thick, lush, and high-growth grass in very wet conditions. The denser the grass and the more moisture, the higher the chances of clogging.

Solutions

Waiting for dryer conditions before mowing can help avoid the wet clumping of clippings that leads to clogs. It’s also helpful to frequently clear clumps of debris buildup under the mower deck as you mow wet grass.

Using a deck washout port to rinse away clippings after mowing can also help prevent clogging issues. Finally, checking and replacing any worn or damaged mower blades can improve cutting and discharge of wet grass.

2. Blocked Air Intake

Gas-powered lawn mowers require sufficient air flow to the motor for proper combustion and operation. When mowing wet grass, the air intake area around the mower deck can get blocked by accumulated clippings.

Insufficient air supply will lead to engine starvation and cause the mower to shut off suddenly. Gas mowers are more prone to this issue compared to electric mowers.

Solutions

By using lawn mower protective covers or screens over the mower’s air intake opening can prevent grass clippings from accumulating and blocking airflow. It’s also important to thoroughly clean wet grass buildup around the mower after each use.

Checking the air filter regularly and replacing it when dirty improves airflow to the engine. Finally, ensuring the engine cooling fins are clear of debris improves airflow over the hot engine.

3. Shorts of Electrical System

Exposure to moisture while mowing wet grass can short circuit the ignition and electrical components on gas-powered mowers. main areas of vulnerability are the spark plug, wiring, and engine ignition areas.

Once moisture seeps into these parts, it can disrupt the ignition sequence and kill the mower engine. Repeated shorting out due to wet grass can cause permanent damage to the electrical system.

Solutions

Using dielectric grease on spark plugs and wire connections helps to repel moisture and prevent shorts. It’s also wise to check ignition parts for moisture after mowing wet grass and thoroughly dry any affected areas.

Installing protective splash covers around electrical components shields them from wet clippings. Finally, waterproofing all electrical connections and the starter assembly prevents moisture damage.

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4. Slippery Conditions

Trying to mow an overly wet and slippery lawn can cause loss of traction for the mower wheels. Spinning wheels on slick grass can cause the mower to shut off due to a lack of forward momentum.

Gas mowers have safety mechanisms that lead to auto shut off when drive wheels start spinning excessively without gaining traction. Similarly, electric mowers require momentum from their wheels to power the motor, which can fail on slippery terrain.

Solutions

Allowing the lawn to fully dry before mowing wet areas can help improve traction and avoid wheel slippage. Adjusting the mower’s wheel position for better weight distribution or adding tire chains provides extra grip on slick grass.

Switching to all-wheel drive mower models can also help traverse wet or sloped terrain. Finally, reducing mowing speed and avoiding sharp turns helps maintain control on slippery grass.

5. Rusting of Mower Deck

Prolonged exposure to moisture from mowing wet grass can cause rust and corrosion buildup on mower decks and blades. This gradual rusting over time leads to friction that can seize up the mower blades.

Rust causes the blades to lose their smoothness free movement and balance. This leads to excessive vibration, noise, and eventual motor shut-off to prevent permanent seizing up.

Solutions

By lubricating the mower deck and blades regularly prevents rust and helps you to maintain smooth operation. Painting or sealing all exposed metal surfaces avoids rust damage. Hand drying the deck and blades after mowing wet grass minimizes moisture contact.

Finally, heavily rusted mower decks and blades may need replacement to restore performance.

6. Lack of Lubrication

The proper splash lubrication process gets disrupted when the underside of your mower deck is caked with wet grass. Lack of lubrication to the moving parts increases friction and drag on the motor.

Without proper lubrication, the motor has to work much harder and can overheat or completely shut down in wet conditions. Lubrication issues will be noticeable from increased noise and vibration from the mower deck.

Solutions

Applying a lightweight lubricant to the mower deck, blades, and linkages before mowing helps maintain lubrication in wet conditions. Using a thinner lubricant that won’t wash away as easily with wet grass keeps all moving parts protected.

Cleaning the underside of your mower deck regularly could prevents the grass buildup so lubricant can freely splash onto cutters. 

7. Dense Grass Buildup

Trying to mow extremely dense and overgrown grass after heavy rains or watering can overwhelm the mower motor and deck. Thick wet grass does not flow out easily from the mower discharge and puts excessive strain on all moving parts.

The motor is forced to draw much higher current while the blades and deck bearings get overloaded. This combination of dense grass and moisture shuts mowers down like driving into a thick jungle!

Solutions

Raising the mower cutting height reduces the density of grass entering the deck which eases strain on components. Mowing frequently prevents grass from becoming overgrown and dense between cuttings.

Allowing the lawn to dry fully before mowing very wet areas avoids bogging down in thick clumps. Finally, frequently cleaning under the deck prevents packed grass buildup from restricting discharge.

Watch how to clean Grass buildup on Lawnmower

Push Mowers vs. Electric Mowers on Wet Grass

Push reel mowers and electric mowers have distinct advantages and disadvantages when operating on Wet Grass. Understanding how both handle moisture will help choose the best option when the grass is less than dry.

Push Mowers Performance on Wet Grass

Push mowers are powered by gasoline engines. They have the power and ability to handle taller, thicker wet grass. The gasoline motor provides plenty of cutting power to slice through wet grass without bogging down or clogging up.

Lawn Mower Shut Off

However, Push mowers tend to tear and shred wet grass rather than cutting it cleanly. This can give the lawn a frayed, brownish look once the grass dries out. It also allows diseases like brown patch fungus to take hold by exposing the inner crowns and roots.

The wheels and underside of a gas push mower will get caked with wet clippings which need to be cleaned afterwards to prevent rusting and clogging. Gas motors may also have trouble starting if the spark plug gets fouled from excessive moisture. Fuel combustion relies on dry conditions.

ProsCons
Strong gas motor provides ample powerTears and shreds blades rather than cutting cleanly
Can handle tall, thick grassExposes grass to diseases like brown patch fungus
Slices through wet grass without bogging down

Electric Mower Performance on Wet Grass

Electric mowers run on battery power so they have zero emissions and are much quieter than gas motors. They are a great option for small to mid-sized lawns under half an acre. When used on wet grass, electric mowers have less power but provide a cleaner, more precise cut.

Robotic Lawn Mower Shut Off in Wet Grass

The lighter weight of electric mowers also allows them to glide over the top of wet grass rather than dig in. This prevents ruts in the lawn once it dries out. Electric motors are fully enclosed and designed to withstand wet conditions without shorting out.

However, you need to be careful not to overdo it and overload the motor cutting extremely thick or tall wet grass. The clippings can still clump up under the deck. It’s best to mow once initially, then make a second pass once the grass has dried to get an evenly manicured look.

ProsCons
Provides a clean, precise-cutLess power than gas mowers
Glides over grass to prevent ruttingCan’t handle very tall/thick grass
Quiet operation with no emissions

How to Safely Mow Wet Grass Without Clogging

It’s a common dilemma for homeowners: you need to mow the lawn, but the grass is still wet from rain or morning dew. Should you wait for it to dry, or is it okay to mow wet grass?

As you may know, there are risks to mowing wet grass which have already been discussed above. However, with certain precautions, you can safely mow wet grass with both electric and push mowers.

  • Raise the blades: Adjust the mower deck to the highest cutting height setting. This helps prevent clumping by allowing more clearance for wet grass to pass through.
  • Take it slow: Don’t rush through the job. Push the mower slowly and steadily to maintain control. Make double passes if needed.
  • Start at the edges first: Mow a border around the outer edges first. Then work into the middle of the lawn in back and forth rows. Avoid sharp turns.
  • Clean as you go: Periodically stop mowing and use a stick or plastic tool to scrape wet clippings off the deck. This prevents buildup.
  • Let it dry: If the grass is very wet, mow only half the lawn and then wait a few hours before finishing. The drying time will allow you to safely finish mowing.
  • Weed whip first: Use a string trimmer to cut down any tall, bending grass around objects and edges. This avoids bogging down the mower.

Conclusion

Mowing wet grass can be a tricky business for any lawn mower. The wet grass causes the lawn mower engine to shut off. So understanding the unique challenges of wet conditions created for both push reel and electric mowers allows you to take precautions. When possible, it’s always best to wait for dry conditions before mowing. But if you must cut wet grass, take preventative steps to limit problems.

FAQs

Should you bag or mulch clippings when mowing wet grass?

Bagging is preferable to contain excess moisture and allow better discharge. Mulching wet clippings increases clumping under the deck.

Does morning dew count as wet grass for mowing?

Yes, it’s best to wait until the dew has evaporated before cutting. Even morning moisture can lead to some clumping issues.

How long should you wait to mow after a rain?

Wait at least 2–3 hours after rain before mowing to allow drying time. Mowing too soon churns up soggy clumps.

Should you mow wet grass at a lower setting?

No, raise the blades higher. Lower settings with dense, wet grass will overload the mower and lead to clogging.

Can you damage a lawn mower by repeatedly mowing wet grass?

Over time, wet grass mowing can lead to rust, clogged airflow, fouled spark plugs, and excessive wear. Avoid it when possible.

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