Upgrading belt drive pump

What is the largest GPM pump I could upgrade to with a Honda gx 390? It currently has a 4 gpm 4200 psi belt driven.

Probably 100 gpm if you turned it into a trash pump. For pressure washing the formula is
GPM x psi / 1100 equals hp

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@Innocentbystander Pressure x PSI? What pressure? Isn’t that what PSI stands for?

I’m old, tired and lying in a motel bed lol. Check my edit


@Innocentbystander Gotcha. Lol, I was confused

You can gain either pressure or GPM with that motor, but not both. It go for gpm

That was my plan. I was hoping to get an 6 or 8 gpm pump.

8 gpm would put you around 1600 psi, minus about 300 for hose length. Fine for washing siding but couldn’t run a surface cleaner with it

That really depends on how much money you want to spend. You could run a cat 650 7gpm at 3000 psi with no problem. What are you washing would be my first question?

You could…but you definitely wouldn’t get 7gpm at 3000psi


Cat says you will get that with 18hp at 1000 rpm you just gotta be willing to pay for it

A gx 390 is 11,12 hp.

You are correct I’m sorry I read that and immediately was thinking 630 sorry. I should stick to drinking and reading not drinking and commenting

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Awe heck man. It’s good ,it’s just brain storming ,ain’t like you pinky sweared on you’re life or nothing. …@Firefighter4hire

Lol. I don’t drink and I miss read stuff often

Many have put a 8gpm pump on the gx390 and strictly used it for house washing like IBS mentioned. If you want to use it for driveways as well you’ll have to go with a 5.6gpm pump which will put you at 2200-2400psi depending on hose length. This works for concrete but you’ll have to use a bit stronger post-treat on it.

@Barry1 Thanks for the info. I guess I’ll just stick with the 4 gpm until I have enough to upgrade the whole unit.

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Liar. We all know you Canucks drink Maple Syrup like it’s going out of style.

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Nothing like a cooling off with a bottle of maple syrup after a hard day’s work

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LOL “cooling off”

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