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Generator question

cbrooks999

Sep 30, 2013
4
Joined
Sep 30, 2013
Messages
4
Hi All;

Not sure if this is the right place for this question but hope that someone may have some info.

I need a generator on my boat and don't have room for a standard generator. (120V AC)

I have an old gas generator and everything works except for the gas engine.

I thought I might be able to hook the generator to my boat motor so I can have 120VAC.

Problem is, my engine at WOT runs at 4200RPM. When using the generator I can set it to any RPM but I'm not sure what this will do to the generator or what RPM it would typically run at - I'm guessing 3000RPM?



Question:

What happens if I run it too fast such as 4000RPM??



What happens if I run a little too slow? say 2000RPM?



With thanks.
 

dorke

Jun 20, 2015
2,342
Joined
Jun 20, 2015
Messages
2,342
Changing the speed of the boat motor driving the generator will have 2 effects.
Assuming there is no "control mechanism" :

1.It will change the output voltage,the faster the speed the higher the voltage.
2.It will change the frequency of the output,the faster the speed the higher the frequency.

So a simple direct connection isn't a good thing.
Do you have a controlling /regulating device such as a VFD?
 

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
If you have to use the boats engine to run the generator then fit an extra alternator/battery and a decent inverter instead. There are some quality inverters out there with very stable outputs and a wide range of power capabilities.

The battery will allow you to use some AC supply 'off engine' when required too.

Look through your boat for the high AC power consumption devices and consider changing them for more efficient systems too - this will help keep the AC power requirements within reasonable limits, save fuel and give more battery time.
 
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