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Simpson MSH3125-S Review – Power Washer Insider

Simpson MSH3125-S Review

Our rating: 4.85

The Simpson MSH3125-S is a gas-powered model famed for its sheer power and its ability to leave almost any surface you can think of spotless. Commercial grade and highly durable, it may not be the prettiest looking pressure washer, but it was what a pressure washer was always meant to be.

The review shall be divided into the following sections:

1. Specifications: We review all the nuts and bolts that define the machine’s abilities and limitations
2. Set-up: We see how easy it is to assemble and get it up and running
3. Use: We try out the product and see if it is easy to use and how effectively it can do its job
4. Maintenance: We consider what’s needed for general upkeep of the product
5. Conclusion: We give the final verdict



1. Specifications

As far as raw power goes, no one can dispute that the Simpson MSH3125-S is a heavy weight among pressure washers for the household. It boasts a rating of a whopping 3,100 psi and a 2.5 gpm. This is afforded thanks mostly to the Honda GCV190 OHC engine. The engine itself has a strength of 187cc and is air-cooled 4-stroke. This powerful piece of machinery is built quite compactly thus the washer itself is does not take up too much space.

Honda GCV engine

Simpson runs on an axial cam pump that requires no pump oil to operate. The adjustment of pressure on the nozzle is done through a new piece of technology called PowerBoost which is incorporated into the washer’s system. Engine oil is included in the package.

The 1/4 by 25 ft long poly-braided hose equipped with quick connections is very durable and can withstand a lot of pressure. The ergonomic spray gun comes with a safety lock feature to prevent any accidents.

Simpson heavy duty hose

It also includes 5 stainless steel, quick connect nozzle tips. The nozzles are color-coded as to allow you to tell them apart more easily and identify each of their applications. The steel spray wand allows you to switch the nozzles with ease.

The relatively light weight, pneumatic tires, and welded steel frame adds to the pressure washer’s mobility and overall durability. This washer also comes with never-flat tires

2. Set-up

I encountered some problems when the product first arrived with missing parts. I called their customer support service and explained the situation and they seemed to have their own conclusions. They ended up shipping me the missing parts for free and I could finally begin.

Upon delivery, the contents of the box should include:

1. Pressure Washer
2. Hose
3. Gun
4. Wand
5. 5 Quick connect nozzle tips
6. Detergent siphon tube with filter
7. Engine oil
8. Quick start set up guide
9. Owner’s manual

The SIMPSON MSH3125-S Dimensions

The quick start set up guide elaborates the assembly process and start up in 11 and 3 easy-to-understand steps respectively. There are no tools required at any point of the assembly.

The pressure washer itself is started up by flipping the ON switch and pulling on the recoil starter grip as is usual with most gasoline- or petrol-powered pressure washers. Refer to the operator’s manual for a more thorough explanation on assembly and start up.

3. Use

Like is said, this is an extremely powerful pressure washer. The 3,100 psi truly does it justice as it cleaned anything I could think of. It is capable of cleaning 2nd story house sidings and even peel paint. I found myself enjoying at how quickly I could get rid of the dirt and grime when using the Simpson MSH3125-S.

Be sure to use the appropriate nozzle depending on the task at hand since the water pressure itself is strong enough to do damage to weaker surfaces like wood. I found that after a little high-powered use, it can even leave a dent on the surface it hit directly.

The hose could be longer and a bit more flexible though. The nozzles – which are color coded for convenience – attach to the stainless steel wand easy enough.

Simpson power washer in use

Like most gas powered pressure washers, it’s not a machine you purchase for its silence. Since the engine is exposed, there is absolutely no sound insulation. This, and because it tends to emits some dizzying fumes, the power washer is a strictly outdoor tool.

Looking like an engine on wheels (see above picture), it is not a very pretty machine. But then again looks aren’t everything. The fact that it has a very minimalist approach to its design allows it to be more light weight and this, along with its large pneumatic tires, makes the Simpson MSH3125-S quit portable.

4. Maintenance

The Simpson MSH3125-S general maintenance is elaborated best in its manual. The manual is clear and concise on the washers maintenance requirements so if you buy this product read it entirely before doing anything else. As it is a gas-powered pressure washer, be sure to:

1. Regularly replace the engine oil. Best to do this while the oil is still warm
2. Regularly inspect the spark plug. Clean the area around the spark plug before removal to prevent debris from falling into the combustion chamber
3. Regularly check and clean the air filter and replace if need be
4. Follow the manual’s recommendations on the right kind of fuel and fuel solutions/additives to use
5. Reconnect the spark plug before the following use

5. Conclusion

The Simpson MSH3125-S is without a doubt the product to look for if what you’re searching for is a pressure washer for heavy cleaning. No amount of mess or dirt can withstand its 3,100 psi and its simplicity in design and function is its greatest asset. I swear this thing can probably be used as a water jet cutter.

It can be said however, that it may just be too powerful for simple domestic chores. I found that if you use the machine on untreated wood or a less than sturdy surface, it will leave noticeable marks on the surface and even dents on some places. Luckily the 5 nozzles will help you somewhat regulate the pressure for such surfaces. Also check the contents of the box upon delivery to make sure all the part are there.

The Simpson MSH3125-S is an investment that will not disappoint. If you’re looking for a simple and yet powerful machine that can do the heavy lifting in terms of cleaning, then this will suit you well.

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