I currently am running a 5.5 gpm machine and its great. However I was thinking about building a 4gpm as a backup. Does anyone know if an 6.5 hp motor will do fine with a 4gpm pump? The reason I’m wanting to use an 6.5 is because I already have it sitting in my shop. Thank you
It’ll work for house-washing. You’ll be limited to around 1,700 psi or so.
The formula is kicking around somewhere, but from memory, these are the common configurations:
4@4000
5@3000
5.5@2500
8@1700
PSI times GPM divided by 1100 equals needed horsepower
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So a gx390 should be able to handle 5gpm at 3000 psi no problem?
Honda rates a GX390 at 11.7 horsepower. 5gpm at 3000psi requires 13.64 horsepower, if you divide by 1100.
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I’ve seen it advertised as 13 hp but good point.
Of course 4gpm at 4000 psi would require 14.5.