Check out there website, www.udorusa.com I think… look under the gear driven pumps and it tells you what size motor you need to achive the specs on them pump, there service is awesome Randy at the service department is always eager to help
If you’re looking to use it for all flatwork I’d go with the Udor 5gpm pump with gearbox. 3k psi is good plus you’ll lose a few 100psi through the hose. The General 5.5 is great and is best for housewashing but lacks the psi for all flatwork.
Barry, that probably won’t work on the GX390. It neds 16hp to put out those numbers. Even the Udor 5gpm/3000 needs 14.5…the GX only puts out about 12-13hp.
Udor cost more but they are bulletproof. Udor did a test where they ran a pump dry for about 6 hours with no issues. I had an udor with over 4k hours, never rebuilt or repacked. The side cracked. They replaced the pump for free, put my old pump in a new casing for free and thanked me for years of supporting them. They will Outlast any engine mated to them twice over.
Why do you think many gx390s are paired with a 4k psi / 4gpm pump? Those numbers “technically” don’t work with a gx390 (4000x4gpm)/1100=14.5hp. But yet everyone has them. It’s the same with the very popular General HP5535 which many have here (even me) paired with the gx390 rated at 5.6gpm and 3500psi. But the psi drops to about 2500 psi.
That 5gpm Udor pump will work with a gx390…of course he’s not going to get 3500 psi but could get in the high 2000s