Lawn mower shaft size. Are Lawn Mower Engines Interchangeable? (Solved & Explained! )

Finding the Perfect Replacement Pump for Your Pressure Washer

WRITTEN BY: KATE HUFFMAN [EDITED 2/2023]

So you’re looking to replace the pump on your pressure washer? Well, you’ve come to the right place. Combine our extensive knowledge with our affordable and great selection, and you won’t find a better place to shop for a new pump. Use our fitment chart (which includes clickable links to all our pumps) at the bottom of the page with the following tips, and you’ll have everything you need to find the perfect replacement. Here’s a broad outline of what we’ll be covering:

Engine shaft size and orientation

Step 1: Determine Engine Shaft Size and Orientation

First, remove your old pump and take a good look at the engine shaft. Put a micrometer on it and get an accurate measurement; don’t just eyeball it. This is the single most important part of making sure you get the correct replacement pump. Most pressure washer engines have a shaft measuring 3/4”, 7/8”, or 1” in diameter. Then take note of whether your engine is vertical or horizontal. Does the engine shaft point straight up/down (vertical), or does it point out to the side (horizontal)? Some replacement pumps can only be installed on a horizontal engine shaft due to an oil ventilation port, so double-check our chart before making your decision.

Step 2: Verify Bolt Pattern

Next, measure the bolt pattern around the shaft, center-to-center. A few power washer models might have twoor even threedifferent bolt patterns around the engine shaft. The most common bolt patterns are the following:

(3 bolts) 7 11/16, 6 3/16, 6 7/16

(4 bolts) 5 1/4, 3 1/4, 5 3/16, 4 1/2

Keep in mind that if your bolt pattern does measure 2 9/16” square, a pump with a bolt pattern of 2 5/8” square will still work for you.

Also, if you have a vertical engine shaft and a three-bolt mounting pattern, note which direction your water inlet and outlet face. If they come out of the front of your washer, you’ll need a front-facing replacement pump, and if they come out of the back of your washer, you’ll need a rear-facing one. Check our chart below to make sure you’re looking at pumps with the water connections oriented in the direction you’ll need.

Step 3: Check Engine Horsepower (HP)

Now that you know your engine shaft size, orientation, and bolt pattern, you should have an idea of which pumps are going to work for your model. Some models might have as many as six replacement pump options. However, some pumps might be too powerful for your engine. If the maximum horsepower of your engine and a pump’s max PSI (pounds per square inch) aren’t compatible, the pump can produce too much pressure for your engine to handle, causing it to bog down or even stall. Check your engine’s maximum horsepower rating and compare it to our PSI chart below:

6.5 HP = 3600 max PSI or less

6 HP = 3100 max PSI or less

5.5 HP = 2800 max PSI or less

5 HP = 2600 max PSI or less

4.5 HP = 2400 max PSI or less

For heavy-duty pressure washers, take a look at our chart below for more HP to PSI details. You can also watch this installation video that will guide you through the process of uninstalling the old pump and installing your new one on your pressure washer. Finally, if you have problems with your pressure washer even after you replace your pump, please check out this helpful Rugged U video on troubleshooting pressure washer issues. You can also see our Rugged U blog about troubleshooting a pressure washer pump after installation.

Midsummer Mower Maintenance ( Bonus Mowing Tip)

Ever wonder what kind of maintenance your mower needs in the middle of summer? You’ve come to the right place.

Where to Find Your Lawnmower’s Serial Model Numbers

Not knowing your mower’s serial and model numbers can be a serious obstacle when you need technical support. Learn the places to find your riding or zero-turn mower’s serial and model numbers.

How to Sharpen Mower Blades for a Better Lawn

Mowing with dull blades is a recipe for disaster—for your lawn and for your mower. Learn how to spot the signs of blunt blades and how to sharpen them.

How to Find Your Pressure Washer’s Model Number

Your pressure washer model number is your key to finding the correct right replacement parts and accessories, but it’s not always the easiest to find. Learn how to locate yours here.

Are Lawn Mower Engines Interchangeable? (Solved Explained!)

Looking to swap out a failing engine but keep your lawnmower chassis? I was wondering the same thing. Is it true, are lawn mower engines interchangeable?

The answer is yes, push lawn mower engines have standard mounting points and can be installed on any gas push mower chassis. The drive shaft and self-propelling accessory drives don’t always align and must be checked.

Yes, riding lawn mower engines have the same bolt pattern and are interchangeable. What may vary includes how the throttle cable is connected, the wiring harness, the pulley system that moves the mower and spins the blades, the fuel line, and in-line filter location, and how the starter connects to the engine.

No electric mower engines vary dramatically and are not interchangeable.

But how much work is required to do this? What’s the cost of a new engine? How much skill do you need?

Keep reading for these answers and more.

Note: If you click some of the links in this article we may earn a small commission at no additional cost to you.

When Should You Change Out Your Engine?

Typical lawn mower engines should last 1,500 hours. If it takes you an hour to mow your lawn and your mowing once a week for 6 months then your lawnmower should last for 62 years at that rate or pretty much as long as you’ll be in the house.

This assumes you change the oil and air filter as required. Follow this maintenance schedule and you should never need to change out your engine:

Cost To Change A Lawn Mower Engine – Is It Worth It?

Is it even worth it to install a new engine? A brand new lawnmower with everything including will run you 100 for a basic low-end model up to 300 for a high-end self-propelled mower. The average runs somewhere between 160 and 220.

A new lawnmower engine from Harbor Freight is currently going for about 99. Assuming it will take you at least 1/2 a day to go over there, buy the engine, take off the old one, and install the new one, is it really worth it?

Yes, there are YouTube videos of mechanics (experienced in this) changing out a mower engine in 15 minutes. But they already had the engine there. They already had all the tools. They’ve done it enough times that they know the ins and outs of making the throttle cable work and hooking up the drive train both to the blade and to the self-propelling system.

Most newbies figuring this out will take several hours if you include the initial trip to buy the engine plus the extra trips to get special bolts, parts, and tools that may be required for your specific engine.

So is it worth it to swamp the motor?

Yes if you have a used motor lying around and you don’t mind spending a few hours swapping them out.

No, if you need to buy a new motor. It’s easier and only slightly more expensive to buy a whole new lawnmower and give your old one to a local mechanic.

Is It Worth It To Buy and Install a New Engine or Just Get a New Mower?

Are Riding Lawn Mower Engines Interchangeable?

Before you change out a riding lawn mower engine ask yourself, can I save the old engine?

• Does it need a new battery?
• Does it need a new starter?
• Does it need a new alternator? The above three could be with a battery/alternator testing kit
• Is it leaking oil or gas? This is where we start to get into reasons to change the engine

• Is the oil pan leaking? Can it be replaced?
• Is it leaking from the head gasket? Can it be easily replaced? If the engine warped due to an overheating and damaged head gasket then you might want to consider a new engine.
• Is it leaking from the carburetor? Can you replace that assembly?
• Is the fuel pump leaking? Can you replace that?

Are Electric Lawn Mower Engines Interchangeable?

No electric mower engines vary dramatically and are not interchangeable.

While there’s an underground movement of converting your old gas mower to an electric one, expect to drill new mounting holes in your current chassis.

If you buy a new electric engine that exactly matches your old one you’ll be OK. Otherwise check the specs and mounting bolt spacing on any potential new engine to make sure it matches the old.

Steps To Change a Gas-Powered Push Lawn Mower Engine

Swapping out the engine on a push lawn mower (gas-powered) is pretty easy. Expect it to take about half a day. Yes, you can do it in “15 minutes” like in the video below.

But that doesn’t include the time to drive out and get the engine, learn how to do all the steps below when you’ve never done them, and go out for extra trips for more parts or tools.

Even in the demo video, they end up pausing it to find nuts that fit the new mounting bolts as they used a non-standard thread.

Expect that to happen and more.

Follow the steps below and watch the video for a demo:

• Remove the blade
• Disconnect the mounting bolts
• Disconnect the throttle cable.
• Pull off the old engine.
• Add the new engine
• Tighten the nuts onto the new mounting bolts. Check that you’ve got the right threading. See mixup in the video below.
• Attach the blade. Make sure it rests in a similar position as the previous one (not too high or low). You may need to add spacers to the mounting bolts to raise it up.
• Attach the throttle.
• Start and test the mower.

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Horizontal vs. Vertical Engines

Drive shaft orientation is one of the most misunderstood aspects of small engines, leading to a lot of fallacies about the advantages and disadvantages of each design. How do you know which one you own? Does one design last more than the other? Is there a reason you should choose a vertical shaft engine over a horizontal shaft or vice versa? Here’s what you need to know to separate fact from fiction.

Model Designations

All Honda engine model names start with two letters to designate their engine family. Currently, this includes the GX and GC. If there’s a “V” after these two letters, the engine has a vertical shaft. Engines that are the same model family and displacement share the same basic design and provide identical performance no matter how the shaft is oriented.

Engine Wear and Lubrication

Myths are persistent about one design wearing out faster than the other, but these can be attributed to a misunderstanding about how these engines work.

Some older vertical shaft engines have the intake and exhaust valves positioned vertically. This draws hot exhaust gases along the bottom cylinder surface, resulting in slightly more wear on that side. This has led people into believing that gravity is a factor, leading to increased wear on vertical shaft engines, but the same wear pattern is found around the exhaust no matter where the valve is positioned.

On the other hand, some people believe that horizontal shaft engines will wear out faster because the upright position of the cylinders keeps them from being lubricated as well as a vertical shaft engine. Both horizontal and vertical engines with splash lubrication use a dipper or scoop to pick up oil in the crankcase and fling it onto the components inside the engine. Even at idle, oil is being flung around the engine at a rate of 20-30 times per second, overcoming any issues with gravity by sheer force. Likewise, while the oil channel location may be a little different, pressurized oiling systems still pump oil up to the head and let it flow back to the crankcase in both engine designs.

Driving Equipment

When engineers choose an engine, they decide on crankshaft orientation based on what makes the most sense to power the equipment. For example, the blade can be bolted directly to the drive shaft on a vertical shaft engine when used in a walk-behind mower, while a horizontal shaft is perfect for the pulley system used on an edger or the impeller in a water pump.

The only time you’ll likely have a choice between vertical and horizontal shaft engines is when you buy a riding mower. Some ZTR manufacturers choose to use horizontal shaft engines to reduce the overall length of the mower, while some older lawn tractors including several of Honda’s own models use a horizontal shaft engine to connect with the axle using a shaft drive. To connect the horizontal shaft to a vertically-oriented pulley, these mowers use a mule drive. This guides the belt along a pair of pulleys, bending them at a 90-degree angle. These added bends are more efficient and reliable than they sound, but they do complicate belt replacement.

Blurring the Line: Mini 4 Stroke Engines

The GX25 and GX35 are technically vertical shaft engines, but their oiling system is designed to work at any angle. This lets them be used in place of two-stroke engines in handheld devices like string trimmers. These engines also find use in stationary equipment, mounted either horizontally, as seen in Honda’s own WX10 water pump, or vertically to power small augers.

How to Create a Go Kart with a Lawnmower Engine

wikiHow is a “wiki,” similar to Wikipedia, which means that many of our articles are co-written by multiple authors. To create this article, 52 people, some anonymous, worked to edit and improve it over time.

There are 9 references cited in this article, which can be found at the bottom of the page.

This article has been viewed 686,047 times.

Though go-karts traditionally use horizontal mount engines, with a little modification, you can install a vertical shaft lawnmower engine to be the driving force behind your homemade racing machine. Taste again the speed, freedom, and exhilaration of the open road when you convert your lawnmower engine into the go-kart you’ve always wanted.

Removing a Lawn Mower Engine

• It’s best to drain the oil from an engine when it’s slightly warm, as the heat allows for a faster flow than when cold.

Drain the gas. Loosen the fuel hose clamp before you start draining your fuel. You can do so by tracing the route of the fuel hose from the engine to the base of the gas tank. Notice where the hose attaches to your lawn mowers carburetor. [2] X Research source Using your pliers, squeeze the clamp loose and slide it upwards on the hose. Now you can detach the hose and drain your fuel into a bucket.

Locate the throttle linkage. You can usually find the throttle linkage beneath the carburetor. There will be a cable that should connect to the throttle, and by removing the screw that holds the cable in place, you can easily remove the throttle linkage. [3] X Research source

Find the starter. This part is on the side of the engine and will have the shape of a small can. [4] X Research source Electric-start lawn mowers will have a red battery cabled attached. Use a wrench to unfasten the cable from the starter.

Remove necessary nuts and bolts. At the base of your mower engine is the mower house, which is where the engine is seated normally. Using your wrench on the bolt and another to hold still the nut below the mower house, unscrew the bolts holding your engine in place.

Take off the drive belt. You will find the drive belt on pulley on the crankshaft beneath the engine. Incline the engine slightly forward and pull the drive belt from its pulley. [5] X Research source

Remove the engine. Taking the engine firmly with both hands, lift the engine from the mower house and place it carefully off to the side in a safe place.

Preparing to Install

• Larger engines in the 13 to 22 horsepower range, which you can find on riding mowers, may destroy the transmission or kart. [7] X Research source

Pick a suitable go-kart frame. You will want one that can support both your vertical shaft engine and lawnmower gearbox comfortably. Your gearbox should will need to have non-trans axle set-up.

• Most frames have a width that varies between 1/3 and 2/3’s the wheelbase of your go-kart, with wider models giving better stability. [8] X Research source

Assembling the Frame

• Always use proper protective gear when welding. Failing to do so can result in significant harm to yourself.

Put in a floor. A 16 gauge sheet metal piece should be sufficient for the floor of your kart. Using your plans from earlier, drill holes in the sheet for the fastening bolts for your seat.

Weld a brace for your seat. You should brace both outer sides of the go kart frame with flat, 3/16 gauge steel. This is where you will install the bench for your seat.

Assembling the Steering Column, Tabs, and Spindle Brackets

Cut and install you steering column. You should cut a section of 3/4 x 11 gauge tubing and weld it to your steering tabs. Insert an additional 1 spacer loosely by the shaft near the steering hoop, grinding the shaft slightly near the hoop if too tight. Drill a three hole pattern with the holes equidistant from the center of the washer at the end of your shaft.

Add resting tabs for brake and throttle. These 2 long 3/8 diameter tabs keep your pedals in their resting and full forward positions. The closest tab to the center of the frame should be fixed a max of 1/2 after the crosswise piece your to which your steering column is attached. The second tab should be installed 1 3/8 after the first tab.

Attach spindle brackets. You will weld these to the front axle of your go-kart. The spindle should have a 1 clearance above the front axle.

Give yourself a foot rest. Use a 3/8 rod in a vise to bend it with a hammer into the shape of your passenger footrest if applicable. This will keep your feet from resting on tie rods.

Don’t forget your brake Band stud. This stud will serve as the pivot for your brake Band. Weld a 3/8 round bar to the frame 1 1/2 after your axle.

Assembling Motor Mount, Brake Rod, and Accessories

• The motor mount should be welded as the final step to building your kart.
• Your mount should be able to hold your lawn mower engine in the horizontal position.

Attach the throttle cable guide tab. About 4 away from the middle of the throttle pedal bolt hole, weld this tab to your kart on a 45 degree angle.

Put in the brake rod guide tab. Take your brake rod and insert it through the tab, bending it to adjust it to the brake Band. Next, take the tab with the rod inserted and weld it to the kart.

Bend your brake rod into shape. Bend this 1/4 round rod so that it angles to meet your brake pedal assembly. Cut the length of your brake rod as needed, and weld eyelets to the rod with a return spring installed brake pedal.

Give yourself a seat. Many go-kart kits do not bolt seats directly to the kart. If this is the case for you, use a simple frame and bolt this into the seat braces. Your seat should be cut at a 37.5 degree angle for a 105 degree incline for your backrest.

Weld motor mount and attach accessory parts. Having finished with the body of your go-kart, you can now weld the mount to your frame. Upon completing your weld, you can add tires, seat padding, and all other necessary hardware to your vehicle.

Installing the Vertical Motor and Gearbox

Bolt down both motor and gearbox to the mount. The location of your motor is not as important as that of the gearbox. [9] X Research source To properly install your gearbox, align it with the gear on the rear axle, and then bolt it into place.

Change the sprocket size for the gearbox. A sprocket is a gear toothed wheel inside your gearbox that controls the gear ratio for your transmission, which is another name for the gearbox. Your target gear will be about 16 teeth.

Attach a throttle cable to throttle linkage on carburetor. Now you can clean off any residual oil from your kart, but do so with care. Always allow for sufficient time for the materials you are working on to cool, like the engine or solder, before using a cleaner.

Community QA

Speed mostly depends on three factors, engine RPM, tire size, and gear ratio. So that question is not easily answered. Most 5-7 HP yard go-karts go 17-35 mph, with 25 mph being common. 8-13 HP go-karts with torque converters and large tires top out at around 40 mph. Race karts can go much faster as they use modified or two stroke engines that rev higher, so you could see speeds of 50-60 mph in those. Enduro and high end race karts can go much much faster.

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As long as the engine is from a decent brand (and therefore good quality), it won’t explode out of nowhere. You’d really need to damage it to make it explode.

Thanks! We’re glad this was helpful. Thank you for your feedback. As a small thank you, we’d like to offer you a 30 gift card (valid at GoNift.com). Use it to try out great new products and services nationwide without paying full price—wine, food delivery, clothing and more. Enjoy! Claim Your Gift If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even 1 helps us in our mission. Support wikiHow

Thanks! We’re glad this was helpful. Thank you for your feedback. As a small thank you, we’d like to offer you a 30 gift card (valid at GoNift.com). Use it to try out great new products and services nationwide without paying full price—wine, food delivery, clothing and more. Enjoy! Claim Your Gift If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even 1 helps us in our mission. Support wikiHow