Hi All:

On my last trip the low pressure feed pump for the water maker (BP pump in French parlance) failed to start.  I measure the capacitance on the start/run capacitor in the engine room and found it to be 4 mfd  .  I happen to have a spare Dessalator supplied BP pump that I purchased when the boat was new (15 years ago) and the specification printed on the original capacitor from that pump, as well as measured with my capacitance meter is 10 mfd (microfarads).  I used the capacitor off the new replacement pump to install on the motor that wasn't running and now all is running.  

However, I note that Bill Rouse of BeBe fame posted in the photos section a specification of 12 mfd for this capacitor.   After being unable to source a replacement capacitor in the USA that has the mounting stud on the top of it and wire leads, I contacted Dessalator.  Rosyne replied that they do not have the stud mounted capacitors available but also mention that the specification should be 20 mfd 370 volts.   ????  Should it be 10, 12, or 20 mfd,  Does it matter which one?

I am pretty good with DC circuits but motors and their run/start capacitors have always been a mystery to me.  Any of our experts out there care to speculate, hypothesize, elucidate the proper specification?

Sincerely, 

Gary S. Silver

s/v Liahona  Amel SM #335    Puerto Del Rey Marina,  Puerto Rico