Things to Know About Marine Generators

Marine generators (or gensets) aren’t cheap, but the sheer amount of electricity-sucking equipment found on boats these days makes them a necessity. 

Getting stuck on a boat out in the middle of nowhere without power isn’t something anybody wants to experience, and marine generators help ensure that doesn’t happen. Here are 10 important things to know about marine generators.

Generator or Inverter 

Do you need to go through the expense of buying a generator, or would a far less costly inverter serve your needs? An inverter takes DC power from the boat’s battery bank and inverts it to AC power. While an inverter doesn’t provide as much power as a genset, if you only require a few thousand watts of electricity when the engine is running, an inverter might be enough.

Boat Space

Marine generators are large and require additional components such as fuel lines, coolant pipes and exhaust ducts. Make sure there’s enough room in your boat to install the generator and its components. Ease of access to the genset for service and repair is also an important consideration.

Power

Choose a genset that runs on the same fuel (diesel or gasoline) as your boat to eliminate the need for a second fuel tank and additional fuel lines. Some generators rely on the boat’s engine to supply the power via a hydraulic pump. Generators using hydraulics as their power source are cheaper than engine-driven gensets, but can’t run unless the boat’s main engine is also running.

A marine generator must produce enough power so that it’s running at no more than 80% of its total output when supplying all the electrical devices drawing power from it. However, the generator shouldn’t produce so much power that the combined draw on it is less than 25% of its total output. 

Operating Speed

A genset must run at a specific RPM speed to produce electricity at 60Hz, which is the frequency for standard electrical supply in the U.S. Slower gensets are quieter but produce less power, while faster gensets produce more power but are noisy. Some marine gensets come with sound enclosures and vibration isolation mounts to reduce noise and vibration within the boat.

Cooling

Marine gensets are cooled by either directly drawing raw water, a keel cooler, or a heat exchanger system. Raw water systems are cheap but prone to corrosion; keel cooler systems are expensive but don’t corrode; and heat exchanger systems are mid-priced and experience some corrosion.

Safety Systems

The more built-in safety features on a boat generator, the better. Look for safety systems such as automatic shut-off for low oil pressure, low coolant flow, high coolant temperature and high exhaust temperature.

Price

A marine genset is a significant investment. Keep in mind that the $200 you saved by buying a smaller generator might not be worth it when you discover the genset is overworked and can’t supply enough power. Choose a generator that will supply all of your boat's power needs, even if it costs more to buy.