I have two Simpson 4200/4gpm machines both with the GX390. I want to swap a pump on one of the machines to a 5+GPM pump. I was recommended this pump: https://www.stealthpressurewashers.com/shop/pressure-washing-accessories/gear-drive-plumbed-pumps/general-hp5535-slap-happy-fully-plumbed-pump-5-5-gpm-3500-psi-3/
The salesman said I would be putting a lot of strain on the engine getting 3500 PSI out of that pump. I told him that with the GX390 you can only get about 2500PSI. I kind of lost faith in his knowledge afterwards. The pump looks good and fits my budget at the moment. With the gear drive and it being fully plumbed, is it a simple 4 bolt project and lining up the shaft key?
The GX390 will run this pump fine? Is there a better option for me to swap to? I have a 100 gallon buffer tank at the moment.
I was in a similar situation last year. Stripped the engines off of two DeWalt machines and skid mounted them. One with that HP5535 and one with the Udor that Alex linked. Both worked fine with no issues. With the Udor you need an inlet fitting and an unloader. With the GP you need to change the inlet fitting, bypass the unloader to the tank, and block mount the unloader. I didn’t notice any major performance differences with either one as far as flow for house washing or pressure for surface cleaning (only residential stuff). So, all things considered, I believe the Udor will outlast the GP, you get your choice of whatever unloader you want, and you don’t have to undo anything (getting the unloader off the pump was a major pain because of the threads having locktite).
Now, I built an 8gpm Udor gear drive on a gx690, run with that and the 5gpm Udor as my Frontline machines, and still have the GP around as a spare.
OK. Sounds like the Udor would be a super simple switch with just needing an unloader and an inlet fitting.
Line up the keyway on the engine shaft (can be a pain but no biggie really), four bolts, 1/2" mpt x 1" barb for inlet, unloader and unloader block, two wire jumper hose from pump, 3/8" mpt x 3/8" barb for bypass, air hose or something else for your bypass line.