How To Troubleshoot a Lawn Mower That Revs Up and Down
Have you ever experienced a situation where your lawn mower suddenly started revving up and down? If yes, you might have wondered whether it is possible to troubleshoot this issue, and if possible, you must have thought about how to troubleshoot such a problem.
Firstly, gather up all the necessary tools and materials. Now, inspect the current state of the Spark plug, Fuel system, Air filter, and Fuel Filter. Next, remove the full Carburetor setup to clean, repair or replace the faulty elements and reinstall everything.
Keep reading the following article and learn details of how to troubleshoot a lawn mower that revs up and down.
What Causes the Problem?
A lawn mower might rev up and down due to faulty or blocked airflows. The most common reasons behind mower aggressive revving trouble are defective spark plugs, faulty spark plug lead, clogged air filter, and fuel filter.
Issues with fuel lines, fuel tank, wrong carburetor adjustment, or faulty internal elements of the carburetor can also cause your lawn mower to experience surging or revving problems.
However, it is hard to confirm any specific culprit without performing a thorough inspection.
Therefore, continue to check on every potential part or internal component until you reach the core of the main issue.
Steps to troubleshoot a Lawn Mower that revs up and down:
When the lawn mower lacks a sustained speed due to insufficient fuel or air, it will encounter aggressive revving issues.
This mostly ends up with the mower engine shutting down abruptly while operating.
It is a common issue that most lawn mower users encounter as their mower gets older or due to a lack of regular maintenance.
As soon you encounter such commotion, you should immediately check what went wrong and fix the problem. Otherwise, this issue can eventually cause more damage to your mower.
To guide you on that task, I have prepared a quick and easy DIY method of troubleshooting a lawn mower revs up and down.
Things needed to troubleshoot a lawn mower revs up and down:
Before moving to the step-by-step troubleshooting procedures, have a proper glance at the checklist of the required tools and materials:
|Standard Mechanical tool box||New Spark plug lead (if needed)|
|Carburetor throttle body cleaner||New Air Filter (if required)|
|Safety Gloves Goggles||New Fuel Filter (if necessary)|
|Other required internal replacement parts|
Step 1- Check the Spark plug, Fuel system, Air filter Fuel Filter:
First, check whether the gas tank is plugged or fuel has any issue. If this area has any issues fix them and if not, then move to the next part.
These two videos will guide you to troubleshoot your mower fuel system issues:
Next, check the current state of your spark plug and repair or replace it as required.
This video will guide you to check, clean, or replace the spark plug easily.
You should also inspect your lawn mower’s air filter and fuel filter. If necessary, replace both filters and for that, these two videos will guide you:
Step 2- Remove the full Carburetor setup:
You can take pictures of every single step of this particular task so that when you will reinstall everything, you will not make any mistakes.
First start the task by removing the entire air cleaner assembly.
Then, remove all the linkage cables attach to your mower’s carburetor.
Next, turn off your fuel supply or drain your fuel tank.
After that, remove the fuel line from the carburetor.
Or, drain the gas leak from the bottom.
Take these two nuts off and slide the carburetor off the main support ports.
After removing the carburetor, remove the float bowl and float pin.
Also, take the float needle valve off.
You can find the main jet right inside this area where the float was.
The main jet will look like the above image once it is removed.
You will also find the pilot jet from the same area and remove it.
Now take the emulsion tube off.
Remember, you can take off all the above-mentioned parts by using a proper sized flat headed screwdriver.
Step 3- Clean, repair or replace the faulty elements and reinstall everything:
Once you have removed the carburetor and all the connecting parts or elements, it’s time to clean every single thing thoroughly with a Carburetor throttle body cleaner.
Make sure there will not be a single hole or part of the carburetor blogged or clogged and not open.
While cleaning the entire carburetor setup, you can also inspect for the broken or severely damaged components. If required, replace the faulty parts.
After that, put everything back together as they were before and test whether your mower is still having the same problem or it’s working fine now.
If any of the above-mentioned techniques didn’t solve your issue, immediately contact the nearest dealership for professional assistance.
Performing such repairing tasks can be hazardous. Thus, make sure you have enough knowledge and expertise to perform them. Remember to first read your mower’s instructions manual before operating, servicing, or troubleshooting it.
Frequently Asked Questions: Lawn mower revs up and down
What causes a lawn mower to pulsate?
If your lawn mower has suddenly started to pulsate, the most common reason behind this commotion can be a clogged fuel supply, bad/old gas, defective spark plug, or faulty carburetor.
What causes a lawn mower rev to bounce aggressively?
Due to an automatic transmission leak or fluid levels falling, your lawn mower rev can bounce like that.
What causes a lawn mower engine to idle up and down?
The most obvious culprit for causing such trouble is a bad idle air control valve. But to confirm the issue, check the engine light first.
What caused my lawn mower engine to shake at idle?
Weak or broken mounts on the lawn mower engine can cause such trouble.
If you ever experience similar issues while operating your lawn mower, try the above fixing tricks.
Initially, those techniques might seem a bit complicated to perform, but if you have minimum mechanical expertise and follow the steps thoroughly, you can easily get rid of this issue in no time.
If you want the best result, you have to thoroughly follow all the instructions for troubleshooting a lawn mower that revs up and down without skipping any detail. So, keep that in your mind.
The Truth About Electric Lawn Mower Horsepower
For the first time in nearly 20 years, I finally have a real yard to maintain at our new house, after living in apartments since 2000 and then our yardless townhouse since 2007. I’ve been having both fun, and frustration, purchasing lawn and garden equipment! Who knew there would come a time where I’d get so annoyed with lawn mower manufacturers that I’d feel the need to write a blog about them. All I’ll say is that considering the overall topic of my website, cancer support, I guess it’s nice to have some first world problems for a change!
Why Is It So Hard To Shop For An Electric Lawn Mower?
When we moved into our new home in July of 2017, the grass was growing and a lawn mower was the last thing I had time to think about on top of all of the logistics of moving and hectic work schedules. I figured I’d try to be green and buy an electric mower, and save myself the trouble of oil changes and maintenance and all that. Our lot is big for our area at 8800 sq ft, but still relatively small in the grand scheme of things, so how are you supposed to know what you really need with an electric mower?
What makes it difficult to shop for electric lawn mowers is that they only advertise the voltage that the battery and electric motor run at, and not how much power they actually produce. These are two different things. How are you supposed to know the differences between how 20V, 40V, 56V, or even 80V electric lawn mowers perform, compared to what actual gas powered lawn mowers with anywhere from 3 to 6 horsepower will do? It’s apples to oranges, and then you get to the issue of endurance. This is a non-issue with gas mowers, as they typically have more than enough internal fuel capacity for even larger yards, and if you run out you can just refill the tank and keep going. With an electric mower, if you can’t finish mowing your yard on a single battery charge, you either need a very expensive additional battery, or have to wait an hour to recharge the first, which can be a major inconvenience.
Claims of gas-like power or torque of gas, enough battery capacity to cover 90% of yards, and run times of up to 60 minutes or whatever are all incredibly generic weasel words, and highly prone to interpretation and misinterpretation. I guess I thought in my mind that a middle of the range 40V electric lawn mower ought to be enough. Was it? Well, I think you might know where I’m going, but read on to find out!
A 4HP Self-Propelled Gas Lawn Mower BASELINE
In the 1990’s, Homelite was a very reputable company that produced a full range of highly rated gas powered lawn and garden equipment. They don’t have the full line of products that they used to, but they’re still around, and I still remember my Homelite HSB21P4C mower. That’s Homelite Super Bagger, 21, Self-Propelled, with a 4HP gas engine, and a blade Clutch that allowed you to just idle the engine with the blade stopped while you emptied the bag without having to restart the engine. Don’t ask me how the heck I remembered that, but when you’re a kid and can’t even drive yet, getting a new lawn mower is pretty exciting. It was a pretty darned good mower, too. I was worried that 4 HP might not be enough when there were 5 to 6.5 HP mowers out there, but it was never lacking for power. It propelled itself up hills with a heavy bag filled with clippings just fine, and although it may have bogged down at times in taller grass that might have been a bit wet or required you to slow down a tad, it always kept going and never quit. It had just the right amount of power, not too little and not too much. I guess this was what I was expecting out of my 40V electric lawn mower, which wasn’t even self-propelled, and so all motor energy would be going straight to the blades and none to the wheels. Surely this must be enough, right?
MY 40V/4AHr Electric Lawn Mower
My wife knew I was looking for an electric lawn mower as we were moving. She saw this one come up on Amazon Prime Day on July 11, 2017 for just 199 last year and told me about it. It looked good enough to me, and heck for only 199 why not? I took a leap of faith and just blindly hip-fired the mower and jumped on it, hoping it would be enough. Honestly, it’s a great 3 in 1 mower for the money (rear bagging, side discharge, or mulching), but unfortunately it just couldn’t get the job done.
Honda Lawn Mower with a Pulsing Engine
One of the first things I noticed was that it would shut down in heavier grass, and I was constantly tilting it on its side trying to clear all of the clippings out from under the deck in mulching mode. It just couldn’t maintain the blade RPM needed and would stall all the time, and overall didn’t do the greatest job of mowing. Not only did it not have the power to really mulch well, but it also didn’t have the suction to stand our mix of grass and weeds up straight enough to get a clean cut either. It would always leave rows of grass and weeds that would just get knocked over more than cut, and I’d have to end up going at certain areas again from the opposite direction to get a better cut. Even more frustrating was the lack of manual power control combined with all of the irregularities of our lawn. It would leave itself in high power mode as I exited thick grass, and would drop itself down to normal power mode right as I was hitting thick stuff again, and couldn’t stay in sync. What it really needed was a High, Normal, and an Auto power control lever, but didn’t have one.
As far as yard size and capacity, our house is on an 8800 sq ft lot with a front and rear portion, about half of which is mowable lawn. In the late summer and into the fall when the grass wasn’t really growing that much, it would finish the whole yard on its 4 AHr battery with about 25% or less charge left. I knew this was pretty marginal, and I wondered how it would do in peak growing season or as the battery aged and lost a bit of its natural capacity? The answer came this past spring when the grass started growing like crazy. This forced the mower into its high power mode almost all the time, and then it could only do just over half of our yard on a single charge! I had to wait an hour for it to recharge before finishing the backyard, which was annoying. There’s a slot for a second battery right on the mower itself, but they really kill you on these batteries. 100 for another 40V 4AHr battery was a bit steep for me, especially when the mower was already under-powered and not mowing that well in the first place.
Overall I was pretty disappointed. Clearly I needed more mower, and decided to just cut my losses and get another one.
THe electric lawn mower Marketing Weasel Words
I love all of these claims about gas-like power and torque of gas for electric mowers, and how even the lower end gas mower manufacturers are playing stupid games by only advertising the peak gross torque of their gas engines. None of this tells you a damned thing, and since since when did the lawn mower market become so ridiculous with such deceptive marketing? Really? You can’t just be straightforward with freaking lawn mowers? What on earth??
Hey, I have torque of gas! If I apply my entire 260 pound weight to a bicycle pedal with a 1 foot long crank, I’m making 260 ft-lbs of torque. Sweet! So I can power a car, right? Ha! No, because how quickly can I spin that pedal while applying that force to get actual work done? Not that fast. Just like electric motors, human beings make peak torque at 0 RPM, and then our torque curves rapidly fall off from there. How much power can I really produce?
This isn’t rocket science. There’s a very simple formula for this.
Horsepower = (Torque x RPM) / 5252
Lets say I could still apply 10% of that torque at 100rpm. How much power am I making? Per the formula, (26 ft-lbs x 100 rpm) / 5252 = 0.5 HP!! Right. That’s not powering a car, or even a lawn mower. If I go all out in spinning class at the gym, I can hit a little over 1000 watts for a brief and glorious few completely unsustainable seconds, which is 1.34 horsepower (746 Watts = 1 horsepower). In that burst of glory, that comes out to about 54 ft-lbs of torque at 130 rpm (or 47 ft-lbs at 150 rpm). In reality, most professional cyclists can sustain an output of about 280-300 watts for hours on end, which is around 0.4 horsepower.
Gas torque doesn’t mean that you have gas horsepower. And what does gas-like power even mean? If an electric mower really had gas power they could just advertise the horsepower of the electric mower, right? But they don’t, so obviously they’re hiding something. If you hit a patch of thick grass at a given speed, you need a certain amount of power (not torque) to get through it. If your lawn mower doesn’t have enough power, it’s going to bog down or even stop, unless you reduce your power demands on the mower by slowing down, possibly to a crawl, such that the rate at which you’re demanding power to mow isn’t exceeding the amount of power your lawn mower can deliver.
Lawn Mowing Is An Endurance Race, Not A Drag Race
There’s an old saying that horsepower sells cars, but torque wins races. Well, that can be true for automobiles if we’re talking about runs down the drag strip, and getting a nice hole shot off the line thanks to a mountain of torque (and traction). Watch most any Tesla Model S P85D or higher at the drag strip destroying tons of exotic cars, and you’ll see what I mean. Maybe that’s what the lawn mower manufacturers want you to think, and are preying upon consumer ignorance here by advertising gross torque and not even net torque, and are constantly trying to hide the actual horsepower output! Torque alone tells you nothing.
Honda GCV 2 seconds RPM increase
But we’re not talking about drag racing here. We’re talking about steady state mowing with very small engines or motors running at their maximum operating speeds. Horsepower is what’s going to win this race and get your lawn mowed, without having to slow to a crawl to avoid your engine stalling. What happens to electric cars at higher speeds or from 50 km/h rolls? They make a ton of torque (and power) up to a given speed, but after that they just fall off like a rock and get walked all over by cars that don’t necessarily have more horsepower, but that maintain higher levels of horsepower to higher speeds, and thus can do more work at higher speeds. Horsepower is what you need for mowing your lawn, not gas-like power or torque of gas. That’s total BS!
How Much Horsepower Does This THing Really Have?
When it comes to actual mowing performance, all I can say about my 40V electric mower is that it’s nowhere close to my old Homelite 4 HP gas mower that I used growing up, which I guess is kinda what I was expecting or hoping for. To be fair, the manufacturer, which I’m not singling out here or even identifying, never made any horsepower claims about this mower, but it doesn’t even mow like a low end 3 horsepower gas mower would either. A 3 HP lawn mower will bog down when you start running it through thick grass, but will keep going if you’re gentle enough. This electric mower doesn’t bog down in heavy grass, it just stops. It can’t handle it at all. It will get it done, but you have to be exceedingly gentle with it. So based purely on how it mows, I’d say this 40V electric lawn mower has a best of just 2 horsepower!
I’m an engineer, so I figured I’d try to be a little more scientific than just run what ya brung type butt dyno (grass dyno?) type testing. We can get a ballpark estimate of how much power this thing is cranking out based on the energy content of the battery, and how quickly it can drain itself. The battery is a claimed 40V and 4AHr battery which means it should be able to deliver 4 Amps of current for 1 hour at 40 volts. However, while pretty solidly in high power mode, it will actually go through an entire battery in a matter of 15-20 minutes. Let’s say that it has an endurance of 15 minutes in high power mode. That means it’s drawing about 16 Amps of current. 40V x 16 Amps = 640 Watts of power.
Electrical Horsepower is defined as 746 Watts, so 640 Watts is not even 1 HP.
Umm, Houston, we have a problem here.
I haven’t precisely measured how long the battery will drain if the mower is at high power mode the entire time. Maybe it’s 10 minutes? That would be 24 Amps of current and let’s say a peak power of 1000 Watts, or 1KW. And more than likely, 40 volts is just the nominal rating of the battery, and it’s probably running more like 45 volts. And maybe the battery is really more than about 4 AHr, or there’s a variance to the high power mode that you can’t really tell to give it an extra boost when needed, and assume 100% efficiency all around which isn’t true even with electric motors, and blah blah blah.
Even being as generous as possible and making every assumption in favor of this mower that I can, I can’t get the math to work out with this thing having anything more than about 1.5 peak horsepower!
And the reality is that it’s probably really sub 1-horsepower, as I suspect.
Gas like power? Compared to what? A weed whacker??
A Honda GX35 4-stroke 35cc weed-whacker type engine is rated to make 1.3 net horsepower, so there you go. That’s what they mean by gas-like power.
What a friggin joke.
It’s Not Just Electric Lawn Mower Manufacturers
This isn’t just about electric lawn mowers, though. I have to call out gas mower companies too, for the completely misleading claims that they’re making also. What ever happened to the base model 3 HP gas lawn mowers? Well, when you see a gas mower only advertising gross torque and not horsepower, that’s apparently how they market 3 HP class gas mowers today.
A certain gas lawn mower I saw with an unnamed but very well known brand of engine was advertising itself as having 6.75 ft-lbs of gross torque. What the hell is that? Well if you look up the engine directly at the engine manufacturer’s website, you can get the full torque curve in a PDF and see that it’s actually only making 5.25 ft-lbs of gross torque at the operational speed of 3600 rpm that most gas lawn mower engines have always run at. Using the formula, (5.25 ft-lbs x 3600 rpm) / 5252 = 3.6 gross horsepower. Now keep reading the fine print, and you’ll see that’s without air cleaner or an exhaust or small muffler installed, which is absolutely NOT how gas freaking lawn mowers that can kick up all sorts of dust and debris are ever run. That would be like instant death for a mower. The actual power you’ll be getting to the pavement (the grass) is the net horsepower, so figure maybe 10% lower figures than gross. You now have 3.25 net horsepower.
Boy, 6.75 ft-lbs of gross torque at a lower RPM that the mower never operates at sure sounds a lot better, so that’s what they go with these days, and they figure that consumers are stupid enough to fall for it or just won’t know any better. Better yet, if you end up buying something that ends up not working for you due to confusion, you have to buy another lawn mower, and they love that even more. That’s what they want. They want you to be as confused as possible so that you hopefully buy the wrong thing, and then have to buy again. You see how this little scam works? Yeah (bleep) that.
So yeah, I fell for it, but fortunately was only out 199, and now needed to buy another mower. Too much money for another battery for the electric mower that I bought that doesn’t even do a very good job in the first place isn’t Smart money.
Time To Upgrade, BUt What To Get?
Considering I had done exactly zero research on this mower or electric mowers in general and just sort of hip-fired it off of Amazon and hoped it would work out, I was perfectly willing to give another electric mower a chance, now having a much better idea of what I needed. I’m not biased one way or another, and actually kinda wanted an electric mower to work out. They’re quieter and can be stored vertically and take up a ton less garage space, and ultimately are going to have much lower operational costs than a gas. I wanted an electric mower to work for me, so if I was biased at all, it was actually towards getting another electric mower.
I knew that I clearly needed something with more oomph than a 40V motor could provide, and about double the capacity of the 40V/4AHr battery. Based on a read through Consumer Reports magazine online and other reviews, which I should have checked the first time around (I’m a lifelong subscriber to CR), it looked like the EGO 56V self-propelled lawn mower with a 7.5 AHr battery probably would do the trick for me. This is actually the only electric lawn mower that Consumer Reports magazine recommends, and seems to be at a pretty good price point at 499 with the battery and cooled charger included!
At a 40% higher operating voltage and assuming all other factors are equal, this 56V EGO mower might be equivalent to about a 2.0 to 2.5 HP gas mower on its best day or peak power level. That’s still marginal power at best, but it’s important to FOCUS on how well something actually works, and less on the numbers. The Consumer Reports review was pretty favorable, as were a few YouTube reviews, but I actually saw another YouTube video of this mower grinding to a stop in the same irregular grass that I have. Not exactly confidence inspiring. I was already committing to buying a second mower, and would have been kicking myself if this next one couldn’t hack it either. I felt like I needed a mower with both double the power and double the capacity at the same time. I was confident about the EGO having enough endurance, but only 40% more assumed power just wasn’t what I was looking for. I don’t have a big yard, but definitely need the power to get through grass, crab grass, weeds, and other super thick patches of combinations of all of the above that I have, otherwise a mower will just grind to a stop like my 40V electric was doing all the time.
I was torn and could have gone either way between the 56V EGO mower with 7.5 AHr and a base level Honda lawn mower that had a 160cc engine with a legit 4.5 net horsepower that would run all day for 100 less money. I actually have a Honda powered pressure washer that I’ve owned for years now, so it’s not like I don’t already have a small gas can for it, and oil to change once in awhile.
Our homeowners association ended up making the decision for me!
Electric Would Have Been Fine, but My HOA inadvertently Convinced Me To Get Gas!
This is now a funny story, but yes, my homeowners association mistakenly cited me for grass that was too long, even though I had just mowed it literally hours before we started getting over a week of solid rain. Yes, the grass got quite long, but adding injury to insult, the alleged inspection came during all of the rain when nobody could mow. I was already pretty pissed off about falling prey to deceptive and misleading marketing practices and needing to buy another lawn mower, and now I was double pissed off about being hassled by our HOA, not yet realizing it was a mistake and meant for another property.
My 1.5 horsepower on the best possible day electric mower would have absolutely choked on this grass after all of the rain we got. It literally has weed-whacker levels of power, which explains quite a bit! I would have had to raise the deck height all the way up, and probably run through the battery a few times, and mow a few times just to get it back into HOA spec. Needless to say, I don’t have time for crap like this, and I especially don’t have the patience to be hassled by our HOA for something so absurd! My wife and I are two busy professionals with two young children at home, a dog, and a disabled person that we care for full time, and I’ve had to travel for work quite a bit lately. I just need to be able to mow when I have time to mow, and not think about if it’s dry enough, what the weather forecast says, what time of day it is, or when our HOA might be eyeing our property (we live right across the street from their office!)
So I just said (bleep) it and got a Honda HRX21VKABCDEFG blah blah blah professional grade mower with the bigger 190cc vs 160cc engine, and 5.1 net (3.8kW) all day horsepower rather than 4.4 HP with the slightly smaller engine, and paid 599 for it rather than 399 for the lower tier Honda. Yes, this is total absolute overkill for my yard, but the first time I mowed with it put a smile on my face, and I knew I had made a great choice. It plowed right through even the thickest portions of my tall and still very slightly damp grass with zero bleeps given amounts of power. It has so much power and suction that it stands even the annoying weeds straight up and delivers a nice clean cut. It’s awesome. I can mow whenever I want with my ‘big block’ Honda mower, and if anybody asks me why I’ve gone all ‘eco-terrorist’ and didn’t get an electric mower, I can point right across the street to our HOA’s office, too. 🙂
Ultimately, both I and the HOA realized the mistake at about the same time. This was actually the second fix-it notice that I had received, and there were other fix-it requests on this notice that just made no sense at all, and seemed to fit some nearby properties better. I brought it to the HOA’s attention who had already realized the mistake themselves, and were profusely apologetic about it. It didn’t change the fact that it pissed me off to high heaven at the time, and that I bought fat and happy gas mower because of it. Hey, it’s fate. I was just meant to get a gas mower. 🙂 Even if a better electric would have had enough power, it still wouldn’t have mowed as well with the raw power this gas mower has to stand everything straight up as you mow and give a nice clean cut. Our yard and mixture of grass and weeds is very irregular, which is precisely where extra power comes in handy.
A SUmmary of Electric Lawn Mower Horsepower guEsstimates
In summary, here’s my best guesstimate of actual electric lawn mower horsepower based on some back of the envelope calculations from my 40V electric mower, and comparisons with actual ownership and use of 4 HP and 5 HP gas mowers, watching a few YouTube videos and reading reviews of the 56V EGO mower, and some feedback from someone I know who has an 80V mower.
Less than 40V: don’t even freaking bother. You’re talking sub 1 horsepower here. Maybe there are some lawns out there where this might be enough, but certainly not mine!
40V class: about 1.0 to 1.5 horsepower being as optimistic as possible. Enough if you have nice even grass and few weeds, but consider this the bare minimum, and totally inadequate if you have thicker stuff and/or weeds to get through. You’ll regret it like I did. There’s a reason why none of these lower voltage electric mowers are recommended by Consumer Reports magazine.
56/60V class: maybe about 2.0 to 2.5 horsepower also being very optimistic, but finally kinda like a real gas mower. Although I haven’t used one, they seem to be reasonably powerful and enough to cut through taller grass and some weeds, but YMMV, and the video I saw of one choking on some taller grass wasn’t really confidence inspiring for a 499 investment. Given one bad experience with an electric mower, if this one crapped out on me too I’d have instant buyer’s remorse and kick myself for not just getting a gas!
80V class: I honestly have no idea. The person that I know who has one has never felt like theirs was underpowered, but every yard and perspective is different, and the 80V motors could just be setup to deliver the same amount of power as a 56/60V mower with a bit less current draw from the battery. All other factors being equal, an 80V class mower could maybe be edging closer to 3 horsepower, but who knows? The people who make these aren’t claiming gas power, either!
120V Plug In Electric Mowers: Standard wall outlets in the U.S. are nominally 120V with 15A circuit breakers, but the maximum for continuous loads is 20% below that at 12 Amps, which is just below 1500W (1440W), and why our wives’ hair dryers all have a maximum of 1500W. What’s a few watts between friends? Thus, the theoretical maximum power you can get from a standard outlet for a plug-in electric lawn mower would be 1440W / 746W (per HP) = 1.93 gross electrical horsepower. The reality with all of these electric motors is that they’re not 100% efficient. Assuming 75-80% efficiency, you’re looking at about 1.5 net electrical horsepower at the blades, which is probably a bit better than my 40V mower, as my 1.5 HP estimate for my 40V mower is based on gross consumption and not net power after efficiency losses.
How Much Horsepower Are Those “Gross Peak Torque” Ratings Worth?
What 6.75 ft-lbs of gross torque on a gas engine comes out to
The very well known small engine manufacturer that I called out earlier, and whose initials perhaps not ironically are BS, is only advertising the peak gross torque rating of their engines these days. They have a bunch of engines, but here’s the actual peak net horsepower at 3600 rpm of their engines that I had to hand calculate from their datasheet, because they don’t want you to know. Net figures include the.10% correction going from gross to net.
150cc. 6.25 ft-lbs gross TQ at 2600 rpm but 5.70 ft-lbs @ 3600 rpm = 3.5 HP net163cc. 6.75 ft-lbs gross TQ at 2600 rpm but 5.25 ft-lbs @ 3600 rpm = 3.25 HP net163cc. 7.25 ft-lbs gross TQ at 2600 rpm but 6.00 ft-lbs @ 3600 rpm = 3.7 HP net
Yes, isn’t it interesting that one of the engines with higher advertised peak gross torque actually has LESS peak horsepower than another with less torque? This is because the torque curve drops off like a rock on this engine at higher RPM, and thus it’s less powerful while mowing your lawn with the engine at its high RPM operating speed! This is why advertising lawn mower engines by their peak gross torque ratings at engine speeds they never operate at while mowing is so freaking stupid and totally misleading.
It’s so stupid that I managed to get pissed off enough at just how intentionally deceptive and misleading lawn mower manufacturers are being that I felt the need to go on a big rant and write this blog, but here we are, and here are my final thoughts.
ELECTRIC: If you want a pretty good electric lawn mower with a nice combination of both power and endurance, the EGO 56V 7.5AHr seems to be the sweet spot for both of those as of 2018, which is probably why it’s the only electric mower that’s been recommended by Consumer Reports magazine. I probably would have gotten one of these if it weren’t for the mistaken citation by my HOA.
On a final side note, I saw a customer review at the EGO site claiming that this lawn mower out-performed a 6.25 horsepower gas lawn mower. Uhh, with a new blade? And was it running properly? Were they actually running it at full power, unlike certain neighbors of mine that I constantly hear running their gas mower at idle while trying to mow their lawn? (I’m not joking!) Let’s say it actually had the same 5.1 net horsepower as my Honda, and assume 100% efficiency. That’s an output of 3.8kW, which would require 68 amps of current from the 56V battery. Based on the energy content of the battery, you would have 6 minutes of run time at that power level, and it would be smoldering hot when you were done. You would need 4 gauge wiring to handle that much current, which is what they might typically put on large electric furnaces for homes!! Call me skeptical, but this isn’t passing my sniff test at all. I’m sure it’s a great mower, but I can pretty much guarantee you that it doesn’t have anywhere close to 5 or even 6 horsepower, or even gas mower power, and they don’t even claim that it does!
I’m pretty darned sure that this person surely must have confused horsepower with the peak gross torque rating of their gas mower, and that it actually only has around 3 horsepower. That would be far more believable and make sense!
But anyways, the EGO gets a recommendation from CR and a lot of positive reviews elsewhere, so I’m sure it’s a fine mower.
GAS: For gas mowers, I would just get a Honda. The base Honda mowers are very good and highly rated at Consumer Reports, and 4.4 net horsepower is more than enough power. I’m extremely pleased with my 5.1 net horsepower (3.8 kW) Honda HRX21VKA. It will plow through anything, at any time, no questions asked, and with zero bleeps given, and has a solid warranty. It ran right through my super tall grass at full speed, and probably has triple if not quadruple the power of whatever my 40V electric mower has just based on mowing performance alone, so I know my estimate and calculations of about 1.0 to 1.5 HP peak for my electric is probably pretty accurate.
Another thing I like about Honda is that they’re actually being HONEST, and publish the full power and torque curves for the engines, and in NET horsepower and torque rather than gross. Unlike a lot of the other manufacturers, Honda has a very powerful brand name to stand behind, so perhaps they can let the quality of their products and engineering speak for itself, and don’t feel the need, or like it would be beneath them, to resort to cheap lies, dirty tricks, and lying by omission to sell their product. In a world filled with so much BS, I appreciate a company that’s honest. Thanks, Honda. There are cheaper gas mowers out there from reputable brands that I’m sure do a perfectly good job of mowing, but I can’t recommend the products of companies that are marketing their goods in such stupid and misleading ways, even if they work OK in the end.
I hope this helped!
Don’t lie or mislead about technical things to an engineer, because they’ll find you out and call you out! I really can’t believe all of the shenanigans going on in the lawn mower industry, and that I felt the need to write a blog about it, but this is just plain ridiculous. How on earth did the lawn mower industry become so freaking dishonest and misleading? What in the world?? No standards, no shame, but considering the overall topic of my website, it’s nice to have some first world problems to rant about once in awhile. 🙂 Honda is actually being honest, and so I’m happy to give them my money.
If you’re someone who has more technical information about these things, or better ability to test them than I do with insights to share, get in touch. I’d love to hear from you.
APRIL 2020 UPDATE
For awhile this has been the #1 blog on my entire website, and it gets thousands of hits per month from early spring through the summer. It’s the first search result for “electric lawn mower horsepower” on most search engines, and I appreciate all of the Комментарии и мнения владельцев and emails that I get. I’m glad so many have found this blog and enjoyed it, and hopefully gotten a laugh or two out of it. So thanks, and I figured I’d post a quick update nearly two years out from this fiasco.
I donated the electric mower to the local Habitat for Humanity Re-Store last year in 2019, so hopefully it went to a good home while contributing to a good non-profit organization, and that the person who bought it didn’t find this blog! LOL!
For the record, I do have a Ryobi 40V string trimmer, that I also got the hedge trimmer, leaf blower, and pole saw attachments for. When it went on sale last year, I also got the Ryobi 40V dedicated chain saw as much for the extra 40V battery as for having a real saw. THOSE I LIKE. They all have an appropriate amount of power, and it’s nice to have a second 40V battery now also. They’re all very nice products, and saves me the trouble of having to have another gas can with 2-cycle fuel-oil mix.
The fire-breathing 190cc Honda “big block VTEC” mower is running great. No regrets on that, but I probably could have saved myself some money by just getting the 160cc model. I was obviously pissed off when I bought the bigger one, but it seriously has “zero fcks given” amounts of power, and it puts a smile on my face whenever I plow through way too tall grass at full speed, and it just takes it. Professional grade, bruh. I bought one for my parents also, the fancier one with the electric start, because their old mower was crap. They love it too and said it’s amazing, and that they can mow their yard in half the time with it, and that it gives them a good workout keeping up with it! Lol! They have a much larger yard, but it’s too hilly and sloped for a rider, so it’s the perfect mower for them. Honda truly makes good stuff.
Thanks again for stopping by and reading!