Hey all, looking for some knowledge here. So I bought a used pw via CL. It is a belt drive M-I-TM machine and has a Honda GX390. The label on the cart says the pump is 3.5/3000. The sticker on top of the pump tho says: “M-I-TM 3-0202”. According to the parts list by M-I-TM, this part number is for a 5.5/3500 pump. Does anyone have any insight on this or any way I can find out definitively which pump is on there? Any input would be greatly appreciated as there is a big gap between the two. Thanks in advance.
You might try getting a 5 gal bucket, crank up your PW, and see how much water pumps into the bucket in a minute. BINGO, there’s your answer.
1 Like
I’m by no means an engine pro, but getting a GX390 to do 5.5 gallons is pretty tough unless you sacrifice PSI. You’re either getting one or the other. There’s a chart somewhere that breaks down the actual psi and gpm you can expect from certain horsepowers.
Two commonly used equations for this:
(GPM x PSI) / 1100 = HP
(GPM x PSI) / 1450 x 1.5 = HP
According to Russ, he prefers the second, giving the reason that the first pushes the engine to the limit constantly.
A GX390 is about 13 HP. So, lets say the bucket test confirms that it is putting out 5.5 GPM. Plug in the numbers, and solve for PSI:
5.5 x PSI / 1450 x 1.5 = 13
PSI = 2285
To compare with the first equation, it results in 2600.
Hey thanks for the replys all. I will do the bucket test and see for sure. If it’s not, looks like I’ll be saving for a bigger machine.
I had another thought that I’d like input on. I haven’t had time to do the bucket test, been in training all weekend and til Tue. MI-T-M makes a 5.5/3500 pump made for my machines setup. Using that pump, it would only get about 2500psi. Would you set the unloader to that or would you just use a pressure gauge to tell and adjust/select nozzles based on what the pressure gauge reads? Or it is lost cause? Upgrading the pump is much cheaper than a whole new machine. Just curious and thanks
I wouldn’t buy a Mi-T-M pump for starters, but that’s because I’ve only seen their machines with AR pumps which means they don’t know much about quality pumps.
1 Like
Set the unloader until only a trickle of water is in bypass when you are spraying. A pressure gauge shouldn’t enter into the scenario. Kinda like adjusting pump packings on a waterous pump
Upgrading the pump isn’t going to help. You can only get but so much from that little engine.
I think he wants to upgrade to 5.5 if he finds out that his pump is only 3.5.
Hooknladder, i have the same engine and i just upgraded from a 4gpm/4200 to a 5.5/2500. Got it from Russ at southside equipment, and it came with an unloader. I’ll post some pics of the process when i get time, but really there isnt much to post… it just bolts right on.
1 Like
To expound on what everyone else is saying, when you set the new pump up, you need the right size tips for the max pressure you’re looking to achieve. 2500psi @ 5.5 gpm requires 7.0 spray tips.
The general HP5535 (formerly ts2021) works well for a lot of guys, myself included.
But if I had a choice of replacement pump, I would go with an Udor. They’re supposedly unkillable.
2 Likes
