There are many valuable or entertaining things you can use a pressure washer to do, like carving a pumpkin and extending the life of your house paint. You can even use a pressure washer like a substitute leaf blower to remove tree debris from your driveway.
A lawn mower is a lot more niche. It does one job. Can you put a pressure washer motor on a lawnmower? I will walk you through the similarities and differences, so you know whether they’re interchangeable.
Despite the engine similarities, you can’t put a pressure washer motor on a lawn mower. A pressure washer engine has a shorter crankshaft, a manual choke and throttle instead of a button, and a keyed shaft instead of threaded. They can even be identical in measurements and still have different setups and features that are not interchangeable.
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Can I Use A Pressure Washer Engine On A Lawn Mower
Putting a pressure washer motor on a lawnmower is not a rookie DIY. With advanced education, precise tools, and skills, you might be able to adjust the power washer motor to fit, but it is chancy and dangerous.
That’s why you don’t see ads for mechanics who will convert engines cheaply. Moreover, a mower is basically a giant powered blade and it is not a good idea to mess with its power source.
Before I explain what part of a pressure washer engine is the biggest problem, please understand that you should never try this at home.
Adapting the crankshaft of an engine is not a good idea unless you know exactly what you’re doing, and even then, it’s still dangerous. You are more likely to ruin the engine than get the right fit for your mower.
A pressure washer engine has a shorter crankshaft than a mower. Your crankshaft, according to Science Direct, “… is essentially the backbone of the internal combustion engine.
The crankshaft is responsible for the proper operation of the engine and converting a linear motion to a rotational motion.”
For some pressure washer engines, there is a metal plate in the way where you would need to connect the mechanism to shut off the motor on your lawnmower.
In short, you could probably put a lawnmower cover on a pressure washer, though it would leave parts of it unnecessarily exposed, but reversing the process wouldn’t fit.
Additionally, the pull-string on many pressure washer engines are on the front. You cannot simply turn the machine around to align it differently.
When your crankshaft is too short, it won’t fit the existing clutch, or you can end up throwing a belt. While there are such things as extenders and shims, playing with the crankshaft that runs a gigantic blade is a terrible idea.
If that isn’t enough to convince you not to mess with your mower engine, then consider the fact that according to The US Consumer Products Safety Commission, “… More than 37,000 Americans suffer a power mower-related injury each year.”
Pressure Washer Motor vs. Lawn Mower Motor
When comparing a pressure washer motor to a lawnmower motor, it helps to start with the same power, model, and year.
Doing this will give you the best comparison between the two and show you exactly why they are incompatible. Sadly, even when you have the same brand, the engines are too different to be interchangeable.
Part of the confusion comes in because the overall size of these two different motors are very similar. They can even be identical in measurements and still have different setups and features.
It may seem like a six-horsepower engine (for example) should work on any machine that requires 6hp, but the placement of the parts and how they attach is very different.
A superb example of this is the fact that a power washer has a manual choke and throttle. Meanwhile, a lawnmower typically has a button for safety.
These two different styles are incompatible, and you cannot simply swap parts within the engine to change the way it works. If you can’t run the throttle, you can’t mow.
For a simple-to-understand comparison, I recommend checking out this Youtube video on the differences between a Quantum 6hp lawnmower engine and a Quantum 6hp pressure washer engine.
Another notable difference is the shaft. On a lawnmower, your shaft is threaded, allowing parts to screw into place. Alternately, on a pressure washer, the shaft is usually keyed.
At best, you would have to manually drill through a layer of hardened steel to adapt the shaft. Even the slightest off-angle could cause massive mechanical failure.
That’s why engines are built in a factory using large, precision machines to drill the holes.
Hardened Steel
Hardened steel is a problem if you plan on drilling, but it is essential for your machine. When steel with medium to high amounts of carbon is quenched after heating, it causes the metal to become tougher.
On the negative side, this hardened steel is more prone to corrosion, but the overall tensile strength is improved.
Especially for an engine where vibration is a significant issue, more rigid steel will help prevent cracks and breakage over time.
Helpful Tips To Know About Using A Pressure Washer Motor On A Lawn Mower
Regrettably, two engines that appear the same on first inspection can be very different. It might seem like a great idea to swap two similar output engines between two machines, but it’s not always possible.
Here are more helpful tips to know about using a pressure washer motor on a lawnmower.
- You cannot safely or efficiently repurpose a pressure washer engine for a lawnmower, but you can reuse it. Some good options for DIY projects you can make with an old pressure washer engine include turning it into a go-kart or making a small hydrofoil RC boat.
- Just as you can’t put the pressure washer’s motor on your lawnmower, you cannot put the lawnmower engine into your pressure washer. You’re better off replacing or repairing machines in the traditional manner.
- It is relatively inexpensive to repair a lawnmower engine. You can expect to pay forty to a hundred dollars, or you can replace it for around the same cost. Meanwhile, take the old motor to a metal scrapper, and you should get five to ten dollars back for your non-working part.
Final Thoughts
Engines can look similar, come from the same brand, and share the same horsepower but still have significant differences.
Unless you are a professional mechanic or an engineer, the disparities wouldn’t be evident at first. However, once you tried to connect a power washer engine to a lawnmower, you would immediately discover the incompatibilities.
Even if you could manage to drill, rig, and hack your way to making the pressure washer engine fit, it would still be foolish and outright dangerous to try and use this sort of Frankenstein-mower.
Instead, trade the broken mower to a scrapper for cash, and sell your functional pressure washer motor to someone who needs it.
You should be able to make at least half the cost of replacing the engine with a new or refurbished model that is safe to use with your mower.