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Are Lawn Mower Engines Interchangeable? Find Out Here...

Written by William
Last Updated on July 20, 2021

If you've owned a mower for a few years, you may find that the power or cutting-effectiveness has dropped recently, and it just isn't what it used to be. This is the case with many mowers, even the very expensive ones- eventually, deck/engine corrosion will take a toll and ruin your lawnmower. 

Throwing your trusty mower out is both wasteful and heartbreaking- so why not switch up the engine to make your mower pretty much brand new again?

To answer your question on whether or not engines are interchangeable for mowers... yes- lawnmower engines are very much interchangeable and will swap with ease- however, the blades and drive systems will differ from mower to mower- this is a critical lawn mower engine point to note.

This article on lawn mower engine changing will cover everything you need to know. 


Ensure Everything Else is Working Fine

This step involves performing a kind of MOT on your lawnmower, to check that everything else is in order. You'll need to check if the other mower components are in good health and are functioning as they should. You will know if anything is abnormal if you've been using your mower for a while now.

One major advantage of this is that if, in the case that your engine is in working order, you'll have spent money on a brand new deck, but still be having issues. In this case, another component of your mower will be the one with issues. Hence, we highly recommend conducting a thorough examination of everything (engine crankshafts, engine specs, standard deck specs, mower oil leaks, the source of mower oil (quality), as well as any general lawn mower engine faults). It'll save you a lot of money.

The engine is a very expensive part of your mower to replace- but you know what's even more expensive? Replacing your engine and discovering that the problem lies with the drive system instead...and then replacing that! Check out the drive system before purchasing a new engine.


Checking Your Engine Health

A lot of the time, your engine won't have faults at all. In fact, many of these common problems occur, and there is no need for engine replacement:

  • Fault in the coil
  • Problem with the carburetor; dirty or faulty
  • A shear-key that is broken
  • A faulty pull-starter mechanism

There are some key things you need to check up to make sure your engine health is evaluated, to help determine whether or not replacement is necessary:

  • Has your gas mower/drive mower/any general mower leaked the oil? Take a look for oil leakages around and beneath the engine- the crankshaft seal is actually a common culprit/source of these leaks.
  • Does your engine start up easily? If your mower is rustier than normal to start up, this could indiciate the need for replacing your carburetor- or it may just need some fine-tuning.
  • Check the oil level- an abnormally high level could again mean there is a carburetor-related issue, while a lower than normal level is a likely indicator that the engine is worn out.
  • Check the oil quality- your oil should never be grey or black; this is a sign you need to change and switch the oil entirely.
  • What is the engine revving like? Does surging happen? If your engine cannot rev without surging, a new carburetor is likely needed rather than a whole engine replacement.
  • In terms of the engine, how would you describe the smoothness? If your engine ends up spluttering or misfiring, then there is a slim possibility that a minor problem is going on with your engine. Fine-tuning may be necessary, but in this case, you'll usually be looking at a much more expensive engine-related repair.
  • Lastly, you'll want to make sure the engine doesn't smoke when you run it- smoke is a surefire indicator of a worn engine, but another likely possibility is overfilling the oil of your engine.

The Drive System Health

The second largest culprit is a faulty drive system. Even if your mower is self-driven, you should check this system up to make sure it's working in order. Some common drive-system problems that may occur:

  • The transmissions are worn out
  • The drive pins are worn out
  • The wheels are worn out
  • The wheel's drive gears are worn out 
  • The belts are worn out 
  • The pulleys are damaged

Here are some key questions to help you troubleshoot any problems related to your drive system:

  • When the drive is applied, do you notice any squealing, screeching, or grinding noises? If not, do you notice any unordinary sounds?
  • The drive application occur smoothly?
  • When travelling up an incline, does your mower need help by manual pushing, or is it capable of travelling up steep angles by itself?
  • When using your mower, is the pulling action smooth and controlled? Or is it broken up and gritty?
  • Is your mower's trans-axle oil-leak free? You also need to ensure that the drive belt of your mower is in good condition too!

Finally... Changing the Engine

There are some key points to note about engine interchangeability, which we'll write below- make sure you read through them all.

All types of lawnmower decks are interchangeable- you can really just move one engine to another, and fit it into the current one. The reason why, is because generally, the engine mounting locations and points are standard for every machine. You can use any deck. However, you need to ensure the new deck is compatible and can work with the other components of your mower. This highly limits the range of other engines you can fit into your mower.

There are mainly 2 options to go for:

  • Your new deck should be identical to your old one
  • Find a second-hand mower with the same engine type (or a different but compatible one) with an engine that's blown- then, you just swap it for the good one. Make sure that the width and lengths of the crankshafts match each mower)
About the author
Written by William
I have always had a passion for gardening and that with a background in selling lawn mowers for the past 10 years, I have become very knowledgeable in all types of gardening tools. The site TheBestMowers.co.uk was created as a hub where I can review and write about all of the tips around gardening.
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