How To Protect Lawn Mower Deck?

Mower decks frequently wear out long before the engines, makes me a little sad truthfully. Deck protection is a chore every mower owner could easily do with just a little knowledge and some elbow grease. I’ve been a mechanic for over twenty years, I’ll show you how to take care of your mower deck.

Protect a lawn mower deck from corrosion in five steps:

  1. Turn mower over, (air filter side up)
  2. Clean deck underside thoroughly with stiff brush
  3. Remove loose corrosion using a wire brush
  4. Cover drive belt with old cloth
  5. Apply thick coat of auto body undercoating

In this post you’ll learn how to safely work on your mower and you’ll also learn how to avoid common mower repair mistakes that can render your mower a no start. If you need video help on this subject it’s all covered here, “Mower deck protection”.

Mower deck

Grass Eats Decks

Mower Repair Safety

Accidental starting while working on your mower, while rare, is possible. To eliminate even the slightest chance, go ahead and remove the plug wire and tuck it out of the way. Your mower plug wire lives right out front of the engine, give it a twist and a pull to remove it.

The mower blade is sharp, so a pair of stout work gloves is advised. A premium mask like 3m is advised, corrosion dust will hang in the air when cleaning. A mask is also required when painting your deck.

Quality safety glasses are always advised, can’t count the number of times they saved me from a trip to the ER. When applying the undercoating, do so in a ventilated area.

Mower deck

Remove plug wire

Tools you’ll Need

You can of course power wash your deck underside, I don’t generally advise pressure washing as power washer pressure is strong enough to penetrate oil seals and remove critical bearing grease.

Water on the electrics and in the carburetor causes a ton of problems too. In addition, you can’t paint the underside until the deck thoroughly dries out. That said power washing is a ton faster than elbow grease, just be mindful of the risks.

If you don’t have a power washer or prefer not to use one, then you’ll require a stiff bristled brush and few paint brushes, for the nooks & crannies. When it comes time to remove loose rust you’ll need a wire brush, alternatively use a cordless drill and a wire brush adapter, works great , saves your energy and time.

Turning Mower Over

Turning your mower over is a simple enough task, sure what could go wrong? There is an incorrect way to turn or tilt your mower. Turning it over incorrectly is a common cause of white smoke or a no start. Tilting it to the wrong side causes oil to enter the combustion chamber.

A mower should always be turned over with the air filter side facing skyward. Your mower air filter lives on the opposite side to the muffler.

Mower on its side

There's a Wrong way

If you have a gas tap, now’s a great time to use it, turning the gas off prevents gas flowing from the gas tank to the carburetor. In addition place a sheet of plastic under the the gas cap and refit the cap, preventing gas leaking from the gas tank.

If you are in any doubt, check out this post “Which way to tilt your mower”, it covers everything you need to know.

Remove the spark plug wire, (if you haven’t already) now go ahead and turn your mower over the air filter side up.

Cleaning Deck

If you are using a power washer, try and avoid directing water at the engine crankshaft seal, drive axle, drive belt, wheels, carburetor, air filter, armature pull assembly area.

Pressure washers may force water into bearings washing away grease and promoting corrosion. Water on the electrics may cause misfiring, no start or premature armature failure. If the electrics do get wet allow them to dry out completely before running the engine.

Not many owners know about the deck wash port. Simply attach a garden hose and run the mower. The spinning blades forces the water to wash the deck, but be warned it leaves quite a mess on the ground.

Cleaning mower deck

wash port

Wd40 helps prevent damp ingress, spraying electrical components before washing may help prevent issues.

If you are cleaning by hand, use a mask, old dry grass may be dusty. Cleaning by hand is a touch tedious but the end result will be worth it. Using the stiff brush on the open areas of the deck, it’s okay to move the blade around out of your way.

Smaller paint brushes are great from the tighter areas. An air line works great to remove debris.

Mower deck rust cleaning

Wire brush works best

Remove Loose Rust

You’ll definitely need a mask for this bit, when using the wire brush, fine rust particulars will hang in the air, you don’t want that crap in your lungs. My top tip is use a cordless drill with a wire brush adapter, fantastic labor saving device, makes the chore almost pleasurable.

If you don’t have power tools, no problem, we’ll do this old school. Use a wire brush to remove loose surface rust and loose paint flakes. We are not trying to clean down to the metal here, just so long as the loose debris is removed we’re good.

When complete, cleanup the work zone, otherwise we’ll get loose debris sticking to fresh undercoating.

Prevent overspray

Cover drive belt & pulley

Prevent Overspray

When painting the deck underside we’ll need to avoid painting a few areas. No need to be too particular, I just use some cardboard or shop rag.

We’ll need to avoid getting undercoating on the drive belt, pulleys and drive axle. Thick undercoating on the belt or pulleys may cause self drive issues. If you do overspray, just clean it off and you’ll be set.

Prevent overspray

One heavy coat

Apply Undercoating

I use auto body undercoating, it protects the deck from corrosion, helps prevent grass sticking and the chute clogging. The undercoating remains flexible which prevents cracking, although your deck is metal, it does flex.

Undercoating is only as good as the surface it applied to, if there’s loose material, oil or the surface is damp, the undercoating won’t remain on the deck. Undercoating products are available for air tools or in DIY style rattle cans. One can is enough to get the job done.

3M make a great product and it’s conveniently sold and delivered by Amazon.com.

Undercoating mower deck

allow 24 hrs to dry

With all prep work done and mask on, apply one thick coat, you may need to contort yourself to nail the areas concealed by the position of the mower. The sides and the chute are the most important areas to coat, use up the whole can as the product goes off after a few hours.

Likewise, if you’re using a spray gun, clean immediately after use. Allow 24 hours for the undercoating to dry completely.

Nice work, your deck is now protected for years to come. Don’t forget to turn gas on, remove gas cap plastic and refit the plug wire.

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Auto Technician and Writer at | Website

John Cunningham is an Automotive Technician and writer on Lawnmowerfixed.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.