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The Best Marine Water Heaters for 2023

Fact checked by William Hart

Your boat is your home. Just as how you invest the effort and time in your house to make it a home, your boats deserve (and should) get the same attention. Undeniably, boats are very pricey investments, so it is just right to have them equipped with the appropriate equipment, hardware and accessories.

One piece of vital equipment you should have is the best marine water heater. Installing a marine water heater is essential because you would always need hot water on your boat.

best marine water heater

It is worth noting that even though you may go boating in warm weather, having hot water at your convenience is a good idea.

Compared to the energy-hungry residential water heaters, marine water heaters are more convenient and designed to be as energy-efficient as possible. Your heater will work best when you choose the right size and install it correctly to maximize your unit’s usage and reliability.

So how do you choose the right boat water heater with so many options and variations in the market? Let us review some top-rated options available on the market nowadays!

Top 3 Products

Best Overall

Whale 6-gallon Water Heater


Honorable Mention

Whale 11-gallon Water Heater


Premium Choice

Kuuma 6G Heat Exchange


Table of Contents

Best Marine Water Heater Reviews of 2023

1. Whale 6-gallon Premium Water Heater

We have to admit; we’re sold by the name itself already. How can a Whale Premium not be a good unit for your boat, right? This fantastic unit is a 6-gallon capacity of 120V marine water heater with a sturdy double-walled front heat exchanger.

We love the double-walled heat exchange system because it uses the boat’s engine to heat the water. The water gets heated by the engine’s closed cooling system while your boat is running. Its heating process is highly efficient thanks to the, yes, double-walled heat exchange.

Don’t let the word ‘whale’ throw you off, though. Despite its name, this unit is only 13” x 19” x 13”. The Whale Premium needs to be mounted on a horizontal surface. You need to weld the hold-down brackets to its inner tank.

The Whale Premium is specifically designed to withstand weather harsh marine conditions. Plus, they are equipped with the latest technology to ensure energy efficiency and long-term use. For these reasons, there are three types of material for this marine water heater that you can choose from:

  • Galvanized steel

This cover provides good resistance against corrosion. Even though the material weighs more than other types of the Whale Premium, it’s made from solid and durable material. That is important, especially if you do a lot of sailing during hot weather.

  • Stainless steel

We don’t know about you, but we love how sleek and modern anything made of stainless steel looks. Not only that, but it’s also highly functional. So, this unit offers a high level of corrosion resistance while giving your space a modern finish. Besides that, this material is much lighter than its galvanized steel counterpart.

  • White epoxy-coated aluminum

This unit will make your engine room look good. Its white body blends well with your other existing equipment, and it’s well-suited to be installed in many private sailboats’ engine rooms. The hardware of this unit has aluminum coatings, so it offers excellent resistance to corrosion.

The features and benefits of the Whale Premium water heater are, to us, the best in the market. Besides the three materials it’s made from, we also like that it has multiple versions to suit any installation needs. You can choose either a combination of electric/heat exchanger or go with the electric-only model. In terms of its size, you can choose between 120V and 240V.

The Whale Premium is also top-notch when it comes to safety. It is ignition-protected and has an integrated pressure relief valve to ensure optimum pressure level.

And when you get this unit, it comes with a temperature and pressure drain tube. Furthermore, it’s recommended that you get the magnesium anodes to prevent corrosion and extend your unit’s life.

One thing you need to take note of is that this water heater can only be mounted horizontally.
  • Durable and built to last
  • Surprisingly easy to install
  • Heats water much faster than other currently available water heaters in the market
  • Offers options to run with or without electricity when your boat is docked
  • Additional accessories available: Water heater conversion kit and magnesium anodes
  • Can only be mounted horizontally
Overall, with its amazingly competitive price, this unit is worth investing in if you’re serious about getting a marine water heater with a heat exchanger.

2. Whale 11-gallon Premium Water Heater

Another Whale Premium unit that is reliable and highly functional is the 11-gallon capacity model. Even though it’s slightly larger than the 6-gallon model for obvious reasons, you can choose either front or rear heat exchanger with this one.

Compared to the 6-gallon model, this unit is more durable and rugged in its construction. It is built to withstand the tossing of sea waters. Plus, this unit also reliably maintains a large supply of water on your boat.

Just like the 6-gallon model, this unit also needs to be welded with its hold-down brackets. Because this unit is bigger, the White Epoxy casing would make it look more space-saving.

Regardless, its material is still tough and corrosion-resistant. Even though you can choose the casing material to suit your taste and preference, note that the tank is made from aluminum. Buyers have indicated that this unit also makes a good replacement for Atwood marine water heater.

One downside that you can observe with this water heater is that it may need some time to heat the water. Thankfully, you won’t be disappointed with the outcome.
  • Can ensure tough and long-lasting quality and performance
  • Built with an interspersed pressure relief valve and comes with a 100 psi rating
  • Designed with a reliable double-walled front heat exchanger
  • Famous for being an efficient and high-performance model
  • Comes with an ignition protection feature
  • May require some time to heat the water
Again, just like the 6-gallon model, this 11-gallon unit is highly reliable and worth investing in. So, if it is a sure investment for boat owners out there!

3. Kuuma 6G 120V Rear Heat Exchange

Despite its name, the heat exchanger actually does both the job of heating and cooling your water. Much like the ones cooling your engine, its generator simply transfers the heat generated elsewhere to the water inside the tank of a marine water heater.

Choosing whether to consider a front or rear heat exchanger is a matter of installation, location, and preference.

The Kuuma 6-gallon water heater with rear heat exchanger is installed as original equipment on many boats. This model allows you to heat water with AC power when docked, or use engine heat when underway.

Furthermore, this version has a smaller water capacity, so it’s suitable if you have restricted space, and/or you don’t usually have many people on your boat. Its heater features a marine-grade aluminum case and a cladded aluminum tank to protect your unit from harsh marine conditions.

Just like the 11-gal. model, this unit’s 1500W heating element also comes with a big diameter two-loop heat exchanger. Due to its smaller water capacity, we found out that this unit heats water much faster than the 11-gal model, so that’s great news if you’re in quick need of hot potable water.

Since this is a rear heat exchange model, the port is located at the rear of the unit, which is located on the opposite side of its potable water input-output ports. We strongly recommend the use of magnesium anode to extend the life of your Kuuma 6-gal. rear heat exchange unit.

Even so, it would have been better if the kit also offers anything additional, just like other available options do.
  • Built with marine-grade aluminum casing and cladded aluminum tank
  • Heats water quickly and built with high-temperature limiter for safety
  • Uses AC power or engine heat for its heat exchanger
  • Super easy to install
  • Competitive price among other marine water heater competitors
  • Doesn’t offer anything additional compared to similar products
By and large, this is the perfect bet for boat owners who prefer a marine water heater that heats the water quite fast.

4. Kuuma 11G 120V Front Exchanger SS

If the 6-gallon water heater is a little too small for you, but you don’t want the over-sized 20-gallon unit, the 11 gal marine water heater should be just the right size for you. Despite its higher capacity than the Whale Premium, this unit only weighs 15 pounds.

While this model seems light, its benefits and functions are as reliable as those of other top-quality marine water heaters. Not only that, Kuuma has been in the industry for a long time, and their products do stand out. Renowned boat manufacturers such as Boston Whaler and Sea Ray have one of these babies installed on their vessels.

There are three main types of Kuuma marine water heaters. You can choose from the side mount unit with a front heat exchanger or select one with a front-rear heat exchanger. And for any type, you have the option of the 120V or 240V unit.

Compared to the Whale Premium’s heater, the Kuuma’s is slightly larger in dimension, i.e. it measures 16.25” x 16.25” x 23.25”. Among the three types we mentioned, we recommend the 11-gallon front heat exchanger model. Plus, the mounting arrangement can either be front or rear, making it versatile to suit your space.

The Kuuma’s heating element has a big diameter two-loop heat exchanger that provides two different ways to heat your water. This unit is also ignition protected to ensure its circuitry is safe when used on gasoline-powered boats.

Moreover, to help ensure safe operation, the Kuuma’s has an automatic reset function that limits temperature from going too high. Another great feature of the Kuuma unit that we like is its patented temperature control. This feature keeps the potable water on your boat at a safe 140°F by controlling the coolant flow in its heat exchanger system.

With a safer water temperature, you can avoid the scalding risk while on the boat. This unit is tough as a nail, too, because its casing and tank are made from marine-grade aluminum, so you can be confident that it will weather any condition.

However, do not be surprised if this item’s current price tag is higher than those of other brands.
  • In-front connections for plumbing and electrical for easy installation and maintenance
  • Can be used while your boat is docked or underway
  • 1500W heating element for fast recovery using shore supply or from a generator
  • Built with a patented temperature control system
  • Comes with an appealing look
  • Cost slightly more than competitors’ products
Overall, this water heater is recommended for those who prefer a unit that can weather any condition exceptionally.

5. Kuuma 6G 120V Side Mount Front Exchanger

A side-mount unit is where the installation is on the sides of the unit. This comes in handy if you need to fix a marine water heater in a corner where certain sides are available. In general, its functions and benefits as a water heater system remain the same.

Like a Kuuma 6-gallon or 11-gal model, the side mount model is also made from marine-grade aluminum and has a cladded aluminum tank. Similarly, its 1500W heating element has a two-loop with a big diameter for its heat exchanger, which is on the front. Its plumbing and electrical connections are also on the front side.

Kuuma is a good brand because it is durable and trusted. It is perhaps one of the leading marine water heater brands out there, and in many cases, you could never go wrong with a Kuuma unit.

A feature that always makes Kuuma the preferred brand is how its circuitry is ignition protected. The circuitry needs to be protected because it will not create sparks that could pose a fire risk in an engine room when the unit is safe and contained.

For all that, you need to ensure that you handle this water heater with proper care and regular maintenance if you wish to keep it free from clogging issues and rust formation.
  • High-quality marine-grade aluminum
  • Can guarantee quick water heating function
  • Engineered with high-temperature limiter
  • Heats water through AC power or engine heat
  • Available at a very competitive price
  • Might be prone to rust and inner clogging if not properly cared for and maintained
Ultimately, this option won’t leave you feeling dismayed since it is designed with useful features and functions that make it a great addition to your boat.

What to Look for When Buying a Marine Water Heater


Getting a marine water heater is one of the best investments you can make when it comes to your boating hardware and equipment. There is no denying that the convenience and ease it provides allows you to have ready hot water on board.

However, with so many units available in the market, how do you know what to look for in a marine water heater?

The most important question to ask is how big your boat is? The size of your boat directly influences the size of the marine water heater that you can get. It’s important to measure how much space you have in the area you plan to mount your marine water heater. Once you’ve measured the space, you need to determine if the area is suitable for a rear- or side-mount.

This is because the space available on a boat is often limited, and almost every space is accounted for. When you know what would be suitable for the area, you can decide the best and most appropriate marine water heater for your boat.

The second important thing you need to ask yourself is how many people are usually on your vessel. This is crucial because the number of people on board will determine the capacity of the marine heater you should get.

Logic dictates that the more people you usually have on board, the bigger the marine water heater’s capacity you will need.

Here are some quick facts for you to remember when buying a marine water heater:

  • Electric-Powered or Propane-Powered

Electric-powered models are reliable and tend to last longer. In general, almost all boats now are electrically powered. It reduces the need for the unit to struggle to be powered.

A propane-powered unit is favoured for its quick recovery rate especially at really low temperatures. Plus, a propane-powered unit is known for its lower running cost.

Even though an electric-powered model tends to last longer, propane-powered water heaters, such as the Isotherm marine water heater or the Raritan hot water heater, are known to last long.

  • Size and Needs

This is a factor that needs consideration without having to really explain why. You can’t be buying a bulky water heater because it’s a good one only for it to be too big for your boat.

Plus, the bigger the unit, the heavier it is, and you can’t be adding too much weight to your boat because you’re going to affect its stability. And remember how a unit is going to fit your needs.

If you need one, yet are concerned about the space it can and will take up, consider a tankless water heater for boats, which is much smaller and lighter.

  • Material

Choosing the right material is very important. Marine water heaters are subjected to harsh weather conditions. To choose the right one, you need to consider your boating style and preference.

Are you boating on freshwater or are you an open sea sailor? These factors will influence what kind of material your marine water heater casing needs to be.

Experts suggest that you can’t go wrong with a stainless-steel casing because it’s hardy against almost all conditions and environments.

  • Brand

This is another critical factor to consider. For some sailors, the brand is not the be all end all factor because they prefer to look at a marine water heater’s functions and abilities.

But, on the other hand, there is also a reason why good brands last the way they do. Reliable and trustworthy brands such as Kuuma or Quick are a good place to start. A Quick marine water heater is known for its ultra-modern look, reliability, and awesome safety functions.

  • Marine hot water heater troubleshooting

It is believed that this aspect is one of the most overlooked factors when it comes to the marine water heater. As important as it is for you to do your research before buying one, it’s also important to see if you’re able to troubleshoot any issue with the water heater company.

Other Important Factors to Consider


What is a marine water heater?

A marine water heater serves the same function as a residential water heater, i.e. to heat water for cooking or washing up. The difference is that the operating system used in a marine water heater differs significantly from that of your home. Furthermore, there is no wiring involved in using a marine water heater. All it uses are hoses instead of pipes.

A marine water heater can get the power to heat the water in two different ways, either through AC power or marine engine heat. Either way, the power would be minimal and will not disrupt the ignition operation of your boat.

How does it work?

Before you go shopping for the latest and best-selling marine hot water unit, let’s take a minute to review what they are and their basic mechanics. Again, just like any appliance you have in your home, you need to know exactly what you have on board.

A marine water heater can either come built-in with your boat or is installed later as per the owner’s requirements. It is a water boiling system within the boat and comes in different sizes, makes, durability, and pattern. They also differ in features, so you need to individually and carefully consider them.

Marine water heaters are either electrical or powered by propane. These heaters give you instant and also a sufficient amount of hot water. Due to your boat’s limited space, marine water heaters are usually small in design and are lightweight.

These are usually installed in the engine room of a boat or a yacht. Some boats have built-in water heaters, but these are not common and often quite costly. If you happen not to be in the above category, you will have to go further into your pocket to do so. But how then do you go about it?

The heaters are heated from your boat’s main engine heat exchanger or volt powering the heating element. For heat exchanger, the heat is transferred through coils in the heater system, and then the coils heat the water. The volt powering, on the other hand, can be supplied by shore power.

If you get the electric unit, the water heater will use the immersion heaters, which is usually located in the lowest part of the unit’s tank. This is because the water is the coldest in the lowest part of the tank so your unit can maximize its heating element.

The propane-powered unit is specially designed and constructed for the marine environment. It doesn’t need electricity because it only depends on your engine’s performance. This unit comes with closed combustion, so they are reliable and can be mounted almost anywhere on your boat.

The main differences with the tanks are in their casings, sizes, and operating systems. There are also several versions of marine tankless hot water heater available. All these depend on what your needs are, and of course, at times, your budget.

  • Types

Depending on the size and features, there are many types of water heaters you can choose for your boat. Commonly, there are immersion-type, gas water heaters, and solar heating systems.

You can also choose to have a marine tankless water heater, also known as an “on-demand” water heater. Since your boat water heater unit is exposed to harsher conditions than your home unit, many manufacturers make them resist corrosion through the special casing.

The casing is made from stainless steel, aluminum, or metal storage tanks to protect them from salt water and air.

  •  Installation

Marine water heater installation is generally not as complicated as installing your home unit. For one, the unit on your boat doesn’t have to use pipes because marine water heaters use hoses. So, you don’t have to worry about any plumbing works on your boat.

Installing your sailboat water heater correctly can help maintain its wear and tear and make sure it’s working at its best. When installing a marine water heater, some concerns are its location, water hoses, and engine flushing.

One of the key aspects you need to consider is the stability of your boat. That is why it’s crucial to select and know where the unit should be installed. Since water is heavy, the tank of your unit needs to be mounted low in your boat. The unit should also be close to your main engine so that the heat loss is less.

Installing or replacing a water heater for your boat requires some handy basic skills. Such basics will help you make the right decision on how to do it right. Unlike a residential water heater that uses pipes, a marine unit uses hoses. So, there’s less headache and less work, to be honest.

And, if you’re trying your hands at it for the first time, all marine water heaters come with a manual complete with an installation diagram.

  • Maintenance

The maintenance of your marine water heater depends on your boating frequency and your unit’s usage. On top of that, you have to consider if your unit comes with additional accessories like a magnesium anode or a conversion kit.

These components may need to be replaced at regular intervals. You will have to pay closer attention to your marine water heater maintenance after its warranty expires.

What are the different types of marine water heater?

Marine water heaters don’t often come in too many different forms. It tends to be quite universal to make installation an uncomplicated work. But generally, marine water heaters can be categorized into the following aspects:

  • With or without tanks – Depending on the size of the space available, you can choose a marine water heater that has a tank or is tankless. A tankless water heater takes much less space, but not too favoured by many boaters because it often malfunctions.

A marine water heater with a tank, though quite bigger, is a much better investment because it has a more efficient water heating system.

  • Capacity – The capacity of a marine water heater is one of the most distinct differences. Marine water heaters usually come in either 6-gallon, 11-gallon, or 20-gallon.
  • Voltage use – The common AV voltage for marine water heaters is 120V or 240V.
  • Heat exchanger – There are two types of heat exchangers in a marine water heater, i.e. front or rear.
  • Mount – A marine water heater can be mounted in several ways. To suit the area it’s going to be installed on the boat, a marine water heater can be mounted either from the rear or side, and some marine water heaters can be mounted either horizontally or vertically.

Because of their convenience, there are many marine water heaters that are available in the market. As any good sailor would’ve done, you would have read countless marine hot water reviews because you wouldn’t want to be stuck with a low-quality unit that does not do its job well.

There are various things to consider before getting your unit. Things such as your boat’s scale, what you use your boat for, or how many people are usually on board. These things will determine the size you need to get.

Many boaters find the 6-gallon marine water heater sufficient for washing up and domestic uses. But if you have a larger boat or more people on board, the water heater can go up to 20 gallons. So again, you need to know the scale of usage before you’re ready to buy one.

Why do you need a marine water heater?

If you’ve been boating for some time, you’d understand how there are times you just need some hot water. Whether for potable use or washing up, hot water always comes in handy when you’re away from shore or out in the open sea.

Other than that, if you like to go boating during winter, then there is no need to tell you what a blessing warm shower can be.

If you’re considering whether to install a marine water heater on your boat or not, here are some good points you can think about:

  • Comfort

In many cases of marine water heater users, comfort ranks number one in their reasons for getting one. As mentioned, you can readily have access to hot water onboard even though you’re underway.

  • Hygiene

Some people prefer to shower in hot water because it removes dirt and grime better. Let’s face it, after a long day of boating under the sun, and with the salt from the sea air on your face, a warm shower is almost heaven-sent.

  • It’s quite an affordable convenience.

With advanced technology and more efficient energy-saving functions, marine water heaters are now more affordable.

Coupled with the fact that it is a good convenience to have on a boat, many boat owners and serious sailors don’t think twice about installing a marine water heater on their vessel.

  • User-friendly

Unlike a residential water heater, a marine water heater is surprisingly user-friendly and easy to install. It doesn’t need any in-wall plumbing or wiring like a residential unit does and it doesn’t come with many complicated components to confuse you.

It’s also easy to maintain and service. In fact, many boat owners install a unit by themselves.

Frequently Asked Questions


What are the most trusted marine water heater brands?

As you would’ve known by now, the market is overwhelmed with a large number of water heaters and making the right choice can be a little daunting task.

There seem to be so many things to consider before you buy one. Granted, some boats are preinstalled with a good water heater unit. So, it’s common to ask which the most trusted marine water heater brand is.

  • Atwood
  • Raritan
  • Quick USA
  • Whale
  • Kuuma
  • Isotemp
  • Torrid

Keep in mind that because these brands are the most trusted marine and boating equipment manufacturers, their products can be and usually are slightly more costly than other brands.

However, many boaters are more than happy to pay the extra price for the guarantee, durability, reliability, and quality these brands offer.

How to install and use?

Many marine water heaters are pretty easy to install. It comes with detailed yet simple-to-follow instruction manuals. In fact, many boaters prefer to install the marine water heater themselves.

However, you can still opt to hire someone from the marine water heater company to install the unit for you. And when once installed and you need to use it? Simply turn it on and wait for a short while, and voila, you will have hot water!

How to care and maintain?

Like any other boating hardware and equipment, you will need to check any appliance on board regularly. Many marine water heaters come with a warranty, so you can always get help with any issue or request any component replacement if something happens.

Since marine water heaters are built to last and withstand harsh marine conditions, they’re pretty tough and hardy, so reports of malfunction or damage are not common.

However, if your unit comes with any additional accessories that require regular replacing, it’s a good measurement to have a proper schedule and/or reminder to have them checked. It is more important if you frequently use your marine water heater.

Is the water used on the boat recycled, and if not, what happens thereafter?

At any given time, enough freshwater must be maintained. Maintaining the supply requires some kind of storage, which is normally provided in any given boat. How you use the water will depend on the number of occupants.

But, such water must be replenished from time to time. Depending on the boat size, some boat owners have had to increase their storage tanks to a large capacity. We would like to point out that as responsible boatowners and boaters, we must ensure to protect marine life by not releasing unsafe water into any marine ecosystem.

It’s a wonderful aspect that the manufacturers give a lot of consideration regarding any kind of waste produced by boat owners, as well as the use of water and any waste.


A marine water heater is an investment worth making. You may feel that you will never have a use or real need for it, especially if you’re always boating in hot weather, but having hot water readily available when you’re on a boat is a wonderful blessing.

It cannot be questioned that having the best marine water heater on your boat can be a game-changer to your boating experience. Whether you need it for drinking or cooking, or for washing up, to know that it is accessible to you is a comfort many boaters choose to have.

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