Any engine is going to build up grease over time. Whether it’s a car, a truck, or a boat. Too much of a greasy buildup can be a danger. With an engine operating at high temperatures, there is a potential risk for fire and smoke. These are incredibly dangerous to experience on a boat. For that reason you may be tempted to use engine degreasers and engine cleaners.

In the automotive industry there are many engine degreasers. While it can be tempting to use these on a boat, they’re not always the best option. Engine degreasers for your boat needs to be safe for use. You need to consider environmental safety should any of it leak into the water. It needs to be phosphate-free and non-toxic. It’s also good to get one that is fast-acting and water-based. That’s opposed to engine degreasers that are petroleum-based. Likewise, you need to consider boat safety. Some engine degreasers can be very corrosive. They are safe to use on the steel of an engine, but maybe not other materials. You need to make sure you are choosing an engine degreaser that won’t harm aluminum, fiberglass, and wiring.

If the situation is bad enough, simple soap and water just can’t get the job done. A good quality engine degreaser can make all the difference. Make sure you get something easy to use and non flammable. A heavy-duty engine cleaner doesn’t have to be bad for the environment or your house. You can also get a versatile cleaner that can be used to clean many parts of your boat.

Krud Kutter Degreaser and Stain Remover

Krud Kutter has a proven formula that has made it one of Amazon’s best-sellers. It’s non-toxic, environmentally friendly, and safe for use around pets and plants. It can be used either full strength for tough jobs or diluted. It can even remove oil and tar. Unlike some engine cleaners, this formulation is also odor-free. It’s recognized by the EPA as safe for the environment as well. Very few other engine degreasers can make that claim.

One of the best parts about Krud Kutter is how diverse it is. You can clean up crayon, food mess, and more with this product. That makes it more valuable for your money. A product that is only going to clean your boat’s engine isn’t going to see a lot of use over time.

Krud Kutter cutter is also used for removing dried paint and wax, so you need to be careful where you’re spraying it. While it will cut through grease easily, it may cut through things you don’t want to clean as well. The formulation is very effective. Unlike some cleaners, you can expect squeaky clean finish with Krud Kutter. Krud Kutter may be best engine degreaser to cut through your grease and grime.


Heavy duty cleaner

Diverse uses

Non-flammable and multi surface


Not a concentrated formula

Not a specific engine degreaser

Chemical Guys Signature Series Orange Degreaser

One are the most popular names in the industry is Chemical Guys. Their Signature Series Orange Degreaser is formulated for tough industrial strength jobs. That includes tools and engines. The formula is super concentrated. That means you can use it for incredibly tough jobs as is, or diluted for less intense applications. It’s a heavy duty engine degreaser for industrial strength jobs.

If you have tough jobs to handle, this is a best engine degreaser for you. For more everyday boat cleaning, this may not be the best solution. Although it can handle things like upholstery, oil stains you do need to make sure you dilute it down which may take some time. Recommended dilution for some more sensitive surfaces can be as much as 20 : 1. That shows you just how powerful this stuff must be when you use it undiluted on your engine.


Fresh scent

Fast acting

Concentrated formula


Not a multi surface cleaner without extreme dilution

Dilution means you need a second bottle for mixing

Sea Foam Marine Engine Degreaser

Most cleaners and engine degreasers are general use. This one is specifically for marine engines. For that reason, you can count on its reliability. The formula really does cut through the intense grease and grime you’ll find in your boat’s engine. Not only will it clean your engine, it will also lubricate it.

Most cleaners are spray bottles. Seafoam is an aerosol can. Keep that in mind when you use it because it is flammable as a result. That said, it is also EPA-certified. The fumes are not dangerous to breathe in, and it is still non-toxic. Just keep it away from a hot engine or an open flame. This is a heavy-duty cleaner for serious grease and grime.

This is one of the most popular engine degreasers on Amazon. There are many thousands of positive reviews for the product. If other people’s experiences mean anything to you, you can have some faith in this degreaser. That said, this is petroleum-based. You may not want to use a petroleum-based product for environmental reasons. That’s up to you though.


Cleans and lubricates

Marine engine specific


Can’t be used for general cleaning


Holy Cow Heavy Duty Engine Degreaser

Holy Cow Heavy Duty Engine Degreaser is not organic, but it does have a fresh scent. It is able to stand up to some of the toughest oil stains you’ll find. It transitions easily from kitchen grease to engine grease as well. It is biodegradable, non-toxic, and it is not chlorine bleach or citrus-based. Many of the engine degreasers on the market are citrus-based. That means this is a good alternative in case you have allergies. The formula is also cruelty free, so you know it wasn’t tested on animals. It is phosphate free and water based. The formula may not be industrial strength, but it is strong.


Environmentally friendly

Well priced


May leave residue after cleaning tough stains

Mary-Kate Grease Away Engine Degreaser

Don’t let the name fool you, this cleaner is formulated for tough engine grease. Specifically, for outboard and inboard motors and tools. It works with a simple spray on and rinse off technique. There are no petroleum solvents included in the formulation either. It is also phosphate-free and biodegradable. However, it may irritate skin if you touch it without gloves. In fact, there is a warning that it could burn skin or eyes. It is pricier than some other solutions, but it works very well at what it does.


Powerful formulation

Specifically designed to handle boat engines


Potentially dangerous to use



T-Greaser is from a company called Trac Dynamics. It’s a multipurpose cleaner and degreaser. Solvent free, antibacterial, non-toxic and non-corrosive. It’s also 100% biodegradable and petroleum free. It will also leave no residue after you spray it on. The formula mixes an emulsion cleaner with organic solvents. Even diluted the stuff works pretty well at cleaning up grease on your engine. The scent is not overwhelming either.


Great for really tough grease stains


May leave some film after tough cleaning jobs

Star Brite Sea Safe Cleaner/Degreaser

Star Brite’s Sea Safe Cleaner and Degreaser is specifically designed for boats. The formula is environmentally friendly and biodegradable. That means you don’t need to worry too much about it if some happens to leak out from your bilge by accident. Just remember, you don’t want to have anything leak out if you can avoid it. You could be facing fines if that happens. In general you want to be using a different product to clean your bilge.

This cleaner is good for getting your engine clean and more. It can even clean up fish blood if you’ve been cleaning some trout on the boat. Like many other cleaner and degreasers, this one is citrus-based. That makes it natural and nice smelling. It also won’t remove any polish or wax.


Safe on wax and polished surfaces

Pleasant smell


May require additional applications for tough grease

Spray Nine Earth Soap Cleaner Degreaser

Spray Nine Earth Soap Cleaner and Degreaser a solvent free. It also features a 9.8 pH level which is very mild. It’s good for removing all manner of build-up including grease, oil, carbon and more. It’s suitable for engines as well as ceramic, fiberglass, and even countertops. You can also use a pressure washer to apply it if you want to.

In terms of being environmentally friendly, Spray Nine Earth soap is biologically based. That means it’s made of renewable agricultural material. Although the formula is proprietary, it is made from corn, vegetable oil, and sugar. Obviously you need to do your best to not allow any of your cleaning products to get in the water. That said, Spray Nine Earth soap will cause some of the least damage to the environment if it does leak out.


Environmentally friendly

Effective on many surfaces


Scent isn’t as nice as some of these citrus cleaners

Simple Green Industrial Cleaner and Degreaser

Simple Green Industrial Cleaner and Degreaser is listed as safe and non-toxic. It’s free from bleach and solvents. That means the formulation is non-toxic, non-abrasive, and non-corrosive. It also features a lemon scent instead of the heavy chemical odor. While it can handle industrial cleaning, it’s even safe for home use. You can use this to clean up countertop, sinks, carpet, and upholstery.

On the industrial side, Simple Green is used in everything from food processing to mining. With the proper dilution it’s safe to use around food. That means you shouldn’t have to worry about using it on your boat.


Diverse applications

Environmentally friendly


Offputting odor

303 Marine Citrus Cleaner and Degreaser

303 Marine Citrus cleaner and degreaser can handle numerous cleaning jobs. It’s safe for use on plastic, fiberglass, painted surfaces, and chrome. The formula is free from alcohol, ammonia, and solvents. It’s listed as safe for use on all water safe materials. You can also use it to clean the surfaces exposed to the sun and it will protect them from UVA and UVB rays.

Unlike some cleaners, it will not leave an oily residue behind. The smell is pleasant but not overpowering. Even tough greasy and dirty buildup breaks down fairly well with this degreaser. While the instructions indicate you can just spray on and wipe off, you may need to do a bit of scrubbing. It will rinse off clean, however. And the lack of chemical smell that you find in petroleum-based cleaners is an upside.


Easy to use


Good smell


Can take a bit of elbow grease

Things to Remember

Anytime you’re cleaning something on your boat you need to consider the environment. There are steep fines for polluters on the open water. Aside from the financial concerns, you should want to keep the waters you boat on clean. Polluted waters aren’t good for anyone. With that in mind, you need to be aware of what your cleaner and degreaser is made of. Also how effective it is and how to use it. The best engine degreaser checks more than one of these boxes.


Phosphates are found in many places. However, you don’t want them in your cleaners. In aquatic environments, phosphates can cause excessive algae growth. If the concentration of phosphates in water is too high it can be disastrous. Excess phosphates will cause excess plant growth. That intern sucks oxygen out of the water. That will kill all fish and other aquatic life in an area. For that reason, it’s best to avoid phosphates in your cleaners as much as possible.


Cleaners that are made with petroleum-based ingredients are also bad for the environment. These products are not biodegradable. They also rely heavily on fossil fuels. And petroleum-based products are also flammable. A spill of petroleum-based products on the surface of the water could light on fire. That said, a petroleum-based cleaner can also be very effective. They are often fast acting and industrial strength. Between water based and petroleum, it really depends on your needs.


The best engine degreasers have a mild scent or no scent. That’s not true for all of them. Some claim to be scent free still have a noticeable odor. Others, generally petroleum-based cleaners, have a very strong chemical smell. This is something to consider if you’re working in a closed space on your engine. You don’t want to be overwhelmed by the odor. A concentrated formula will usually have a more intense scent. The best choice is often a mild one.


When you’re concerned about cost, you need to factor dilution into your equation. Some cleaners are good to go as they are. Others require heavy dilution. A formula you need to dilute will last a lot longer but it may cost more. The best choice for you depends on your needs. A good degreaser can ideally work on multiple surfaces. Make sure you know the proper dilution of the product before trying to clean grease and oil stains.


You could make a good argument that an engine-specific degreaser is a good idea. It’s designed to handle tough jobs. Many of these cleaners work better than general degreasers. However, they may not work elsewhere. If you want a cleaner that can do upholstery, fiberglass, and painted surfaces, keep this in mind. You may need to invest in several cleaners if you don’t choose a versatile engine degreaser.


The fact of the matter is not all cleaners are created equal. You need to check reviews online before committing to any new products. A job like an engine takes more work than your kitchen counter. You need to know if the engine degreaser you’re buying can handle that level of work. Likewise, is it going to clean completely or leave residue? Some cleaners require multiple applications. Or you’ll need how to use a brush to scrub it clean. And, as we saw, some cleaners can work as is and some need to be diluted. All of these factor into how effective it is and getting the job done. You need to decide how much effort you want to put into cleaning your engine.


There’s a reason we focus on the ingredients in cleaners and degreasers. That’s why being non-toxic or free from solvents and bleach is a selling price. You need a cleaner that is going to be safe for you and for the environment. Many of these formulations can be extremely harsh on skin and lungs. If you’re working in an enclosed space on a small boat, you can become overwhelmed with a toxic cleaner. Your safety and the safety of those around you should be your first concern at all times on a boat. Not just when you’re operating it, but when you’re doing maintenance.

Non-toxic cleaners are always the best bet for cleaning your engine. You don’t want to end up in a hospital as a result of trying to get your engine clean. Look for non-abrasive, non-flammable, biodegradable cleaners. If a cleaner requires you to wear a mask to use it, you may want to search for a better option.