Generator Panel.JPG

Our most important decision in this project is probably the selection of generator sets.  Without electricity, none of our devices are usable and the boat is not habitable.  While we have provisions for shore power along with alternative forms of energy production and storage, the generator sets are the prime movers.  

Fir is currently fitted with two (2) 100KW generators run by Detroit Diesel 671s. The control panel allows for manual synchronization such that the boat is able to produce 200Kw, excessive for our purposes.  Our load analysis indicated a much lower demand for living at anchor and cruising.  We only need 100Kw to comfortably use the crane, and 440V for deck equipment.  We routinely run a 100Kw generator at less than 50% capacity which will strain the system over time. 

The existing Detroit Diesel generators are reliable workhorses even in less than ideal circumstances.  Every diesel mechanic in the world should be able to service them, and parts are readily available.  Unfortunately,  they are absurdly loud, consume more than 5 gallons of fuel per hour, and have a reputation for consuming oil (though we have yet to experience this). 

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After due diligence, we have made several decisions that will guide us in choosing a generator.  First, we will keep at least one of the Detroit Diesels as a backup.  Second, we will only consider new generators that produce 440 volt, 60 cycle, three phase current since changing this would require rewiring that is both expensive and time consuming. Third, we would like to have an automatic paralleling system of two or more generators able to share the load and adjust to prevailing conditions.   In our load calculations, the dynamic demand varies considerably.  An automatic paralleling system will allow us to address this fluctuation. 

Ultimately, we are looking for a durable and dependable replacement similar to the original system. We will retain and rebuild one of the Detroit Diesel generators and use the other Detroit Diesel for parts.  This will guarantee a deep inventory of replacement materials.

Now we need to decide on a generator to replace our retired Detroit Diesel.  Marine generators offer few options between 25Kw and 50Kw.  Load analysis suggests that we can operate at anchor with as little as 12 Kw, but need 20Kw to cruise. However, to cruise, and operate emergency systems we need a total of 35Kw .  In addition, generators function best at 80% of rated capacity therefore we will need to calculate proposed loads and make this adjustment. 

Our search has narrowed down to Northern Lights and Kohler.  Northern Lights makes a well built, user friendly generator with the lowest repair rate in the industry.  They also offer a number of accessories (like a PTO) that could be very useful.  Northern Lights offers paralleling though through their TSC controllers, and add-on accessories (motorized circuit breakers).  The maximum output of the paralleling system is limited to the rating of the smallest generator, therefore Northern Lights system works best with two equally sized units. 

 Northern Lights Generators M844LW3 20 Kw

 Northern Lights Generators M844LW3 20 Kw

Kohler also utilizes sound engines, and are slightly lighter than the Northern Lights unit, yet they do not offer a PTO option.  However, Kohler's Decision Maker 3500 allows paralleling generators of different sizes without purchasing additional equipment, such as motorized circuit breakers.  The Kohler Decision Maker is designed with a software program that will allocate load to the appropriate generator based on need.

Kohler Marine Generators Paralleling Controller

Kohler Marine Generators Paralleling Controller


Model                                   M844LW3                14EKOZD            24EKOZD          32EKOVD

Cylinders                              4                               3                           4                         4

HP                                          32                             24.7                     38.7                     TBD

Weight                                  1,063                        896                      1,078                   TBD

Dimensions                           46X22X28               42X26X28            47X26X28           TBD

KW                                         20                             14                        24                         32

Fuel at Half Capacity           1.00                          0.57                     0.98                      TBD


Check back in a few weeks and learn our final decision.