# Thread: Water pressure and flow rate

1. ## Water pressure and flow rate

Does anyone have any idea what the general water pressure and flow rate is on the incoming 3/4" dia. waterline of the domestic 1200 watercraft when at top end speed? Thanks for any help!

2. Operating Specs

Operating RPM: 7300-7400
Idle RPM: 1350-1450
WOT Fuel Flow: 57 LPH
Idle Fuel Flow: 2.4 LPH

W/In PSI @ WOT 38 PSI

These are specs based on what would have been the 2005 Matrix.

3. Thanks Art...I would have guessed it would have been a little higher but it's good to know. The PSI is more important info right now than the flow rate...but if someone has an idea it would be good to know as well.

4. I would think if you look on the net here there is probably some type of formula to figure out how much flow you have with 38 psi on a 3/4" hose. I don't know for sure, just throwing that out there.

5. Well you could to some degree but pressure doesn't always relate to flow rate. I mean let's say you put a solid plug at the end of the hose so there's no water flow but there's still a water pressure. So assuming the water is flowing through the hose, is the water pressure a result of the resistance of the system or is that the pressure that the pump creates going into the intake tube?

6. You're right. There's probably too many variables. So much for that idea.

7. I seem to recall reading somewhere (no idea where) that the cooling water inlet pressures were in the 40-60PSI range, maybe a little higher.

Can you rig up a pressure test gauge on a running domestic ski, tapped in at the pump base, and go for a short test ride?

I would expect the water pressures would be in the same ballpark for any of the domestic 900+ engines, just a little higher for a strong 1200.

FYI, the water pressures delivered by the speedometer pitot inlet are 30-50PSI at speed (IIRC).

8. Well I met with a local company (Ron-Vik) that makes inline water strainers...as this is what the main question is leading to, and they gave me this general chart for water strainers so I thought I would post it...it doesn't mention based on what screen size is being used but it gives people an idea. From the chart, it's getting to be more important to try and find out in general what the water flow rate is. If the psi in the system is lets say 40psi and it's running 25 gal a minute, since the Polaris intake line would use the 3/4" NPT strainer type, that would be close to a drop of 5 psi in the system...ie. 12.5% pressure drop. That seems like alot to me.

Maybe someone can copy this over to the tech section somewhere....

9. Scott-good info....although, quite a few of us have successfully used the McMaster 3/4" strainers on our triple pipe boats...CrazyA, Beerdart, TxPro, ph20, myself, and some others...Running 2 half inch ones on my ~78mph GPR without any issues. Remember too, that impeller size, engine rpm, nozzle size, boat speed, intake grate, etc will all affect the water flow through the cooling system. You can also reach a point where there is TOO much pressure in the cooling system. I honestly don't feel that the strainers restrict flow to the point where it is detrimental to the cooling of the engine and pipes.

10. I do know many on here use them and have done so without issue...I was just surprised at the amount of reduction...wasn't implying that it's the wrong thing to do. I know that there are a lot of factors involved and one really needs to simply test their own setup for exact numbers but I don't think I will be going through all that. I just like knowing all the facts that I can about something before I make a desicion...the Ole jumping off the bridge thing...although in this particular situation, I really don't think it makes any difference...unless you ride in a lot of water with plant vegetation areas...which I don't but a lot of people do. Yes, there is a point of to much pressure but I think at only 38psi (even if it's 60psi) that it's far from creating a problem and I'm sure Polaris configured the triple pipe system to use the psi pressures that it creates.