Article by Capt. Steve Katz
Today’s modern conveniences rely on household electricity to operate, such as air conditioning, refrigerator, ice maker, cooking appliance, water heater, battery charger and many electronic devices. Many boaters desire or require these conveniences while on-board their boats. At the dock, there is usually a shore power connection available to supply electricity to the boat, and while at sea or in a remote area, a fuel burning generator is the common source of electricity.
We refer to these as generators, they are actually an engine (gasoline or diesel) mechanically coupled to an AC (Alternating Current) generator, also referred to as the generator “back end”. The engine and generator are usually coupled horizontally in-line, but some newer compact units have a vertical configuration, coupled by a drive belt.
Safety
Marine generators have many design features for uses in confined spaces on-board a boat. Off-the-shelf, portable generators for outdoor use at your home or campsite were not designed for use on, or in a boat, and should not be used by boaters. Carbon monoxide poising is always a concern for any fuel burning device and a gasoline generator in the confined spaces of a boat can emit toxic gases that can migrate into living or sleeping spaces, or even to neighboring boats.
If your boat did not come with a generator, adding a marine generator to a boat will require a knowledgeable technician to review your boat to allow for a safe and reliable source of power. Gasoline powered generators can be difficult to retrofit due to the numerous standards and requirements for ignition protection requirements by the USCG and ABYC.
For convenience, a genset that operates on the same fuel as your boat is a good decision. An exception is the popular large, center console outboard boats. These boats do not usually have below-deck provisions for ventilation, wiring and ignition protection for a gasoline powered generator so therefore a diesel generator may be a better choice.
Generators have specific wiring requirements in regards to the neutral and ground wiring, along with a proper power transfer switch allowing the safe switching of power between shore and generator.
Sizes
What size generator do I need? If you are adding a new generator or replacing an existing one, calculating your load requirements is necessary to properly size your generator. Marine generators are sized by capacity in watts, usually kilowatts (kW or 1000 watts) and many marine generators have the kW size in part of the model name, such as the Onan QD 9 , Phasor K3-9.5KW, both approximately 9 kW.
While many electrical devices use a steady amount of power while on, devices with motors, such as air conditioners, ice makers, water pumps, etc can use up to three times their rated power when starting.
The generator must have excess capacity to handle this start-up load or the device will not be able to run. Be sure to select a generator that is larger (by 25% or more) than your total running and surge loads to allow for future needs and to avoid the generator running at maximum capacity. Most generators operate efficiently with a 35% to 70% load.
Installation
Generators need air, water fuel, wiring and exhaust. The most problematic areas of generator installations are the cooling seawater and the exhaust. Generator manufacturers provide installation instructions that need to be followed. Do not assume that the previous installation was correct for a new generator.
Most generator manufactures require a pre-determined amount of drop in the exhaust hose, from the generator outlet down to the muffler inlet. Without the proper drop, water can remain in the exhaust hose and can possibly be forced into the engine when the boat rolls, heels or pitches.
The raw water should be supplied by a dedicated seacock without a high speed scoop, which could allow water to be forced into the generator when the generator is not running, causing internal engine damage. An anti-siphon loop between the generator’s seawater pump and the injected exhaust elbow is needed if the generator is installed at or below the maximum heeled waterline.
Generators tend to be compact and top heavy, requiring the proper mounting hardware. I have seen many generators installed with only self tapping screws, instead of proper thru-bolted, heavy duty mounting hardware. The boats mounting structure needs to be able to support the weight of the generator and provide for vibration dampening that will reduce the noise and vibration throughout the boat.
Maintenance
Most marine generators have all the components of the main propulsion engines, such as a raw water pump, primary and secondary fuel filters, oil filter, drive belts, air filter, etc. These items need to be inspected and maintained as determined by the manufacturer. Some generators have built-in diagnostics that alert you to a problem, often by blinking a code on a diagnostic panel. If you can decipher the codes, it can help you troubleshoot and service your generator.
The generators governor is a very important aspect of its operation. The governor is a device that maintains a constant, pre-determined speed, or RPM of the engine. This is necessary to provide the proper frequency (60 Hz in the USA) of electricity. A generator engine running too fast or too slow will directly change the electrical frequency, possibly overheating or damaging connected electrical devices.
A properly sized and maintained generator will provide years of safe electrical power while on the water or docked in remote locations.
Captain Steve Katz, ABYC Master Technician, is owner of Steve’s Marine Service serving Annapolis and Ocean City, MD.
