hi
I do little powerwashing mostly sewer work. For my purposes 3.8 gpm is not near enough. I use 5.5, would like 8 (heck, would like 20 gpm at 2500psi for mains and culverts but that would be a dedicated rig on a trailer, and I don't get enough of this work to justify the $30k for the machine), but at around 6gpm I start running into supply problems where the supply can't keep up with the rig and need a tank fed rig and I don't want the tank in my van as I am tight on space already.
My (very limited) experience with power washing is that my 5.5gpm rigs at 3200psi will do small jobs nicely and vertical surfaces ok, but get painfully slow on large flat sufaces like parking structure spring washdowns. I would think it comes down to what jobs you intend to take, and size the machine accordingly.
A final note which likely won't apply to you; I live and work at 9600' altitude. Non-turbo engines produce about 70% rated horsepower at this altitude with the thinner air so I have to order my machines with larger engines or buy the engines and pumps and bits separately and build them myself. I have also had to lean out my fuel mixtures to get the engines to run nicely, and would like to find a way to advance the timing a few degrees as this would help as well, but I cant do it thus far as ignition on my engines doesn't seem to be adjustable (no distributor to twist; just the coils triggering off the magnet in the flywheel.....maybe a bracket to move the coils roud the wheel a bit would work by I haven't found the time to do it).
On belt drive vs direct... mine are belt as at the time I built them no direct drive pumps were aval in 5.5 gpm. AR now offers one. I'm building a new rig and will likely go with that pump and a 23hp Vanguard engine (that eng. has are 1" shaft; Honda's in that range are 1 1/8" shafts and the pump is a 1" and dont yet know if I can couple those within the axial constraints of the mounting flange). Belt has its plusses, and is necessary at flows over 5.5 as far as I know, but I will try the direct drive on this rig as it saves so much space.
$1200 sounds fair but look around. I have always found that paying more $ up front for the same machine is well worth it if you get quality, intelligent service and fast parts availability from that dealer as I cannot afford for a machine to be down for more than a day or 3. If I'm buying something big from someone, I call their service dept and ask them questions about problems I don't yet have and see if they have the answers and can get me the parts quick. I like to see how much they seem to know and judge their level of tolerance for brain picking.
good luck!
