While servicing and maintaining the lawnmower is not the most enjoyable DIY job, it is relatively simple, with components being easily accessible and available. It is especially useful for very old machines, which eventually wear out.
Both the mounting bolt screw thread and bolt patterns are the same on all lawnmowers within certain engine power bands. In many cases, lawnmower decks are interchangeable, subject to the crankshaft pinion’s identical length and diameter.
Most manufacturers have standardized the bolt patterns and screw threads across the range. The reason for this is that most manufacturers use several differently sourced engines, even on the same model lawnmower.
Most Lawnmower Decks Are Generally Interchangeable
While there are exceptions, it is normally possible to replace your old broken lawnmower deck with a similar one, even from another manufacturer.
When evaluating whether you can use an alternative deck on your lawnmower, it is important to distinguish the type of lawnmower.
- A gas powered rotary push behind a lawnmower.
- A gas-powered rotary walk-behind lawnmower.
- A ride-on lawnmower.
- A ride on Zero turning radius lawnmower.
A Gas-Powered Push Behind Lawnmower
Push behind lawnmowers are powered by a gas engine that drives a rotating shaft that rotates the blades.
As long as the replacement deck is the same size as the existing one, it can be considered a donor.
Most engines within a specific power band have a similar bolt pattern for the bolt’s engine mounting bolts.
In addition, engine mounting points are generally standardized across all manufacturers; however, this is the only component to which a standard applies. Generally, it is the only part that you can substitute.
It includes components like the
- Lawnmower crankshaft.
- The handlebar mounting points and method.
The Lawnmower Crankshaft
The crankshaft is the spindle (metal drive shaft) mounted at the bottom of the engine and pokes through the deck to which the blades are attached.
As the motor runs, it turns the crankshaft and causes the blades to spin.
The two measurements which need to be the same as the existing lawnmower are.
- The diameter of the hole in the deck through which the crankshaft fits.
- The length of the motor’s crankshaft extends through the deck.
If the hole is smaller, you can increase the diameter by drilling through it; however, you need to ensure that the widened hole remains in the same centered position as the old one.
The crankshaft length is measured from the bottom of the mounting ring to the end of the shaft.
It is incorrect to measure it from the bottom of the oil pan because this may fit slightly differently to the donor deck.
If the length of the crankshaft is not the correct size, it will be difficult to resolve the issue, and you should continue looking for a better fitting donor part.
A Gas-Powered Rotary Walk Behind Lawnmower
It is a self-propelled walk-behind lawnmower.
Each manufacturer’s driving mechanisms are proprietary, so using a different deck for a self-propelled walk-behind lawn mower is not recommended.
If you don’t mind losing the self-propelled functionality, with some modifications, it may be possible to substitute a different deck; however, this is not recommended.
In this instance, it is recommended that you purchase a factory-approved replacement deck.
A Ride On Lawnmower.
Ride-on lawnmowers are the easiest to substitute decks with, as the drive system is composed of a single rubber drive belt.
You may have to call upon your inner MacGyver talents to make some adjustments.
The most likely differences will be in the following areas.
The Mounting Point Dimensions
The deck has to be positioned with the correct longitudinal and latitudinal alignment and ensure the height control is not compromised.
The positioning of the mounting points which hold the deck to the height-adjustable arms of the ride-on lawnmower’s body may be different.
It will have a severe consequence on the quality of the grass cut produced by the lawnmower.
The Ride On Lawnmowers Crankshaft Alignment
The engine has a similar crankshaft arrangement to a push behind a lawnmower; however, it does not have to pass through the deck.
It attaches to a pulley that is attached to the drive belt, which passes over the two or three pulleys attached to the blades.
The only measurement you need to match is the vertical height of the engine pulley to ensure it is perfectly aligned with the pulleys on the lawnmower.
The drive belt measurement
The normal drive belt used on the old deck may not be the same length as needed for the donor deck.
Your lawnmower shop will have various belt sizes which you can try, and if none of them fit, some shops offer a service to custom make drive belts.
A Ride On Zero Turning Radius Lawnmower
While the decks on zero-turn lawnmowers may be interchangeable, the donor part must have all of the features which exist on the old part.
Zero-turn lawnmower decks often include.
- Very specific mounting points fit on the end of a height adjustment lever.
- Have proprietary positioned deck baffles.
- Strategically fitted Anti-scalp deck wheels stop the deck from contacting the ground when passing over a high spot.
With these unique components, and because Zero Turn lawnmowers are very expensive, it is recommended that you only substitute the deck with the same make and model.
Issues To Consider Before Substituting The Lawnmower Deck
The probable reason for wanting to substitute your lawnmower deck is;
- The old deck has been seriously damaged in an accident.
- The old deck has become so rusty and worn over years of service that it no longer functions.
Before deciding on your course of action, check the condition of the rest of the lawnmower.
If you have to replace more than just the deck on the lawnmower, it may become more economical to replace the whole machine.
The State Of The Handlebars
Ensure that the old handlebars are in good condition and haven’t been weakened by years of pushing, pulling, and lifting.
It is very difficult to fix broken lawnmower handlebars permanently.
If the handlebar arms have been weakened, you may not be too far away from replacing them.
Check The Engine Controls
If the controls have stopped working and you have resorted to pushing the levers at the engine, it may be time to call it a day and look at a replacement machine.
Evaluate The Engine
There is no point in relacing the lawnmower deck if the engine is on its last legs.
While you can resolve most engine issues by replacing an air or fuel filter and the spark plugs, as the engine is used eventually, it will require attention.
- Resolving compression issues (rebuild).
- Replacing the starter coil or the shear pin.
- Replacing the carburetor.
While all of these are possible, you should first evaluate the costs of reconditioning against the cost of replacement and the confidence that a new, easily started, a clean-cutting new machine will provide.
Use the below video tutorial to replace the lawn mower deck.
Can I Put A Bigger Deck on My Lawn Mower?
Yes, you can easily put a bigger deck on a lawn mower but always remember that the power of the engine is directly proportional to the size of the deck. Therefore, it is not really advisable.
While it is possible to swop lawnmower decks with others, the optimal solution is to use an identical donor deck that matches your existing one.
Another solution is to source a complete donor lawnmower with identical lengths and widths crankshaft (possibly with a blown motor), which you can swap your good engine onto.