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Why do boats have a diesel generator?

Why do boats have a diesel generator?

A large majority of boats are powered by diesel engines. These powerful machines are typically strong enough to provide propulsion and electricity for the whole vessel. However, these machines are also quite loud and can consume a lot of fuel. While the boat is moving, the main engine runs and powers everything on it.

 However, when the boat stops somewhere, main engines are typically shut off in order to save fuel. There is a drawback there; all the electricity is now provided by your onboard batteries. As with all batteries, their charge is far from infinite. Once the batteries are depleted, you have to restart your engine just to charge them again. Or, rather, you would have to do that if your boat didn’t have a power generator.

How are they different from engines?

Power generators are actually just smaller engines. However, they are called generators due to their purpose. Boat engines’ main purpose is propulsion, and the supplementary function is electricity generation. Power generators, on the other hand, are used exclusively for electricity generation, hence the name. Additionally, they are typically much smaller than boat engines and spend far less fuel. Furthermore, they are far less noisy than engines as well. All of these things make them preferable to engines when it comes to electricity generation.

How strong are they?

There are many different generators, depending on your boat’s needs. Typically, smaller boats will adopt a generator which produces up to 3 kW, since that is their energy need. Larger boats need more power, so a stronger generator will be employed. Something as large as a ferry or a Navy ship will typically have a generator which produces an excess of 25 kW. If you are unsure which generator you need, it is pretty easy to calculate. Add all the power consumers onboard, and you will get the expected wattage. Your generator should be able to power them all. You can also consult an expert for this. 

When are they useful?

Probably the main purpose of the power generator is providing electricity when anchored somewhere without external power supply or somewhere at sea, or are experiencing some main engine issues. As they are considerably better at converting fuel into electricity than the bulky main engines, they will enable you to be autonomous for longer periods of time. Power generators are connected to the boat’s fuel tank, so they do not require any separate fuel supply. Also, with the considerable noise reduction, anyone looking for peace and quiet will definitely prefer this method. Fishermen are known to use these at times when main engines would be detrimental to their fishing.

Navy ship diesel generator

Another group that uses power generators is the US Navy, as well as some other allied nation navies. A large portion of Navy ships are technological marvels, with a lot of different electronic devices. All of these devices require power, so a supplemental Navy ship diesel generator is pretty much standard equipment on most vessels. Submarines in particular need diesel generators as a backup to the nuclear reactor they normally use.


As with propulsion, you can choose what you use to generate electricity on your boat. Diesel is the most common choice since it has a great fuel-to-electricity ratio. However, if you own a gasoline powered boat, you are more likely to choose a gasoline powered generator, since it can be attached to the main fuel line. The newest addition to the ranks of power generators are hydrogen generators. While being fairly safe and ‘green’, the availability of refueling stations poses a problem for their widespread use.

The US Navy has chosen PCE as a partner on multiple occasions when it came to the maintenance of their ships. With over 40 years of experience in the boating and diesel business, we are sure that we can help you with any problem you may have with your boat. Contact PCE today to learn more.

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1620 Rigel Street
San Diego, CA 92113
Phone: (619) 235-0961
Fax: (619) 233-5096 
Diesel & Motor Division
3376 Main Street
San Diego, CA 92113
Phone: (619) 235-0961
Fax: (619) 687-0038 
99-1221 Halawa Valley Street
Aiea, HI 96701-3281
Phone: (808) 486-6600
Fax: (808) 845-1652 
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Everett, WA 98201-1300
Phone: (425) 257-9065
Fax: (425) 259-6851