Genset selection

The term genset refers to an electrical generator used in any type of application. Marine gensets used aboard boats provide power for the AC electrical needs of the boat. Other common uses for non-marine generators are construction sites, back-up power for buildings, and main power for homes located outside power plant distribution grids. While all these generators are basically the same, with the exception of their output, the marine generator has several unique features that set it apart from land-based generators.

The major difference of marine generators is the cooling and exhaust systems used on the unit. These systems will normally contain the same components as a marine engine. More subtle differences will be found in the wiring, controls, and connectors used within the unit. All of these components are built to marine standards that will provide a longer life span in the marine environment.Asking questions

The first step in generator selection, for replacement or a new installation, is sizing the unit to current and future needs. I suggest consulting with a qualified professional before purchasing any unit. They can help calculate the correct output, physical sizing, and cooling and exhaust requirements for the units they carry. It is wise to contact several manufacturers to determine which builds the unit best suited to your needs.

The following questions must be answered before a final decision can be reached:

>· What is the size and the weight of the unit? These issues are critical for its placement in the boat.

>· What is its output? This must be known in order to size the unit to your power requirements.

>· What is the availability of parts? This becomes an important issue if your boat relies on the generator for systems support.

>· How many hours a day will the generator run and will the unit withstand this type of usage? Living aboard and voyaging require different considerations than a weekend boat.

>· What type of fuel does it use? The unit must be fueled by the same fuel the main engine requires. It is a poor choice to use a gasoline generator in a diesel-powered boat.

>· What are the noise characteristics? This is one of the important creature comfort questions. The decibel level without a sound shield and with a sound shield should be investigated. It is not uncommon on many boats for space limitations to rule out the use of a sound shield around the generator.

>· How easy is service access? The unit must have easy service access to check the oil and coolant levels, change the water pump impeller, and change the fuel filter, oil, and oil filter. This access must be equally easy with and without the sound shield in place. If the sound shield must be completely removed to accomplish any of the above, the projects will, most likely, not be completed on a regular basis.

The foregoing is not an all-encompassing list of the questions that must be answered, but it does indicate the installation concerns most often encountered.

The physical size of the unit is dependent on the output wattage of the unit. The higher the output of the unit, the larger the physical size of the unit. Both of these concerns must be taken into consideration when choosing a generator.

In general, if a boat has one 30-amp shore line, the generator should be a 4,000-watt unit. A 50-amp shore line will require a 6,000-watt unit. Twin 30-amp shore lines will require a 7,000- to 8,000-watt unit. As the wattage increases, so does the size of the unit. An 8,000-watt unit may be as large as the main engine. Add to this a sound shield, and the space required becomes a vital concern for placement of the unit.

The weight of the genset will have a direct bearing on the placement of the unit. If the unit cannot be placed on the centerline of the boat, the weight factor is more critical. Placing a 1,000-pound generator to one side of the centerline of the boat will cause a significant list. This amount of list cannot be offset with opposing ballast. Placing the unit too far forward will create a bow-heavy boat. Placing it too far aft will force the boat to squat in the water when it is underway. In this situation the boat may not be capable of achieving a planing attitude while underway.

All the facts above equate to one simple solution: consult a qualified professional before the purchase and installation of any generator.Installation

When the proper unit has been selected, the installation of the unit can begin. If this is not an exact replacement of an existing unit, the only choice is having a professional install the unit. This is not a do-it-yourself project. The equipment, materials, tools and knowledge required to properly install just about any generator is normally beyond the capabilities of the average boat owner.

If this is an exact replacement of an existing unit and you choose to accomplish the project yourself, the following should be considered. The project will require at least two people. You will need a means to lift the old generator out of its location and lower the new generator into place. You will also need the correct tools and supplies to install the new mountings, wiring, cooling, exhaust, muffler, and controls. Follow the manufacturer’s instructional literature for the installation of these. If the unit’s literature does not include a shop manual, purchase, read, and understand the shop manual before you begin the installation.

Generators are the most abused mechanical device installed on board most boats. If the generator is properly maintained and slightly pampered it will run well, but the occasional breakdown is always to be expected. Repairing these breakdowns can be accomplished by most boat owners.

The purchase of a shop manual for your unit and a high-quality digital multimeter are the first steps in the repair process. It is beyond the scope of this article to list all the repair steps of even the most popular brands of generators. Each manufacturer uses different controls and circuitry to maintain the peak performance of their units.

One area many manufacturers now have in common is the use of circuit boards for most of the control functions. If a certain aspect of the unit is malfunctioning, a circuit board change may be the required repair. While this saves time and labor cost, the boards are far more expensive than the old-style contacts or solenoids.

The replacement process for a control board will be relatively simple, consisting of removing one board and installing the new board. The diagnostic process may be somewhat more difficult, but, with the proper meter and a few phone calls to the tech support line, the offending component can be recognized and replaced without difficulty.

After the unit is installed, routine maintenance can be accomplished using the shop manual for the unit and many of the same procedures as are used for the main engine maintenance. Importance of maintenance

There are a few points to remember when setting a maintenance schedule for the genset. If the genset is run only a few hours a day it is easy to forget how quickly these hours add up to the recommended oil change interval. Four hours a day, seven days a week will require an oil change in less than 30 days, if the recommendation is a one hundred-hour interval. Twenty-four hours a day, as with large vessels and commercial boats, will cut that time to every four days. The injectors, if diesel, or spark plugs, if gasoline, must be serviced or replaced regularly, as must the fuel filters. Many manufacturers require the head bolts to be torqued after a certain number of hours along with a few adjustments to the generator portion of the unit. All of these items must be attended to for continued reliable performance.

It is important to remember that the genset is not the main engine. It is often run many more hours than the main engine and therefore must be treated as such. In all my years of boat repair, I have never been aboard a boat to find the generator maintained to its level of abuse. It always appears to be the hardest used and least maintained piece of equipment on board. Portable units

I have not discussed portable generators as they are not a wise choice for most boats. The smaller suitcase units are fine as a back-up for minimum interim power while the main generator is being repaired. This is the only duty for a portable generator aboard a boat. Using a large unit to supply the boat’s AC needs is not an advisable application. These units are not built for the marine environment. They are extremely noisy, costly to operate, and not intended for constant operation.

The final choice for the type, size, and installation of a generator should only be made after the proper questions have been answered. Pushing yourself to a quick decision may be a long process of regrets. Spend the time and money to make the correct decision.

You will never regret the amount spent for high-quality equipment and a proper installation. And after the genset’s installation, you will never regret the amount of time and money spent for maintenance.

By Ocean Navigator