Laid Back Boaters

So after running through several equations, I come up calculating a pressure difference of less than 1psi by changing your nozzle by .25"... under ideal conditions (ie laminar water flow, no heat loss, no flow restrictions like bends and such) if you're moving 4000 gallons per minute you get a 0.437135 psi difference between the two nozzle sizes. I don't think that the small change is going to drastically effect performance.

Advertised flow on Berekely jet 12-j series is "Flows up to 4,000 gallons per minute" if you switched from what you have to a berk style round nozzle with 3.25" diameter at 4000gpm you'd have a 16.7847 psi difference dropping that to a 3" diameter nozzle would give you a 39.6949 psi difference.

The cavitation could be caused by either lack of intake water, lack of exit pressure, or turbulent flow either into or within the pump.
If the water is leaving the pump too fast, or entering too slow however you choose to look at it, it will create low pressure in the pump which will allow the impeller to basically pull vacuum air bubble behind it. This is much the same effect as when you smack your beer bottle down on the top of your buddies, the bottle moves very rapidly down and the fluid tries to stay put. The result is a small vacuum bubble formed at the bottom of the bottle which the carbonation in the barley pop expands to fill causing the beer to then foam over. Inside your pump you have the same thing happening if you don't have enough pressure, the blades of the impeller can basically do the same thing as that beer bottle, and pull away from the water fast enough that the pressure doesn't hold the water into that lower pressure are well enough to keep it full of water, and creates the same void space, and therefore more turbulent flow that causes negative performance effects. This turbulent flow is what rough leading edges cause where the flowing water doesn't get enough of a chance, or have enough pressure to fill in the voids created by the rough spots.

Hope that helps a little bit. I have access to people here on campus that know this kind of stuff inside out. So if you have any questions, I can either try to answer them as best I can, or I could ask some of these professors that I pay oodles and gobs of money to to teach me stuff.

Thanks for better explaining what I was trying to get out of my head and into a post!

Thanks Kona! That kind of information helps a lot! Because it is a Panther, there are a few more variables. Being an Axial Flow as opposed to a Mixed flow. The pressure numbers are lower, but the volume numbers should higher, that is if I am understanding most of the information I've been accumulating. In my little pointed head I see the berk as a garden hose turned up all the way, and a Panther as a fire hose moving similar amounts of water, just at a lower pressure. I think right?

I did check one other thing, in the hopes of a simple, unexpected possibility. I made sure there wasn't a ski rope or tree branch caught in the front of the impeller. There wasn't. So.......on with the testing! LOL!!

you are correct young jedi warrior!

almost a year later and it's still very fitting-

All I can say is you just gave me the best laugh everve had in a real long time lol

All I see is a red X

I'll have you know, I set-up and shot that video on my hour lunch break from work! You think I get excited about boating on Shasta Lake? You BET YOUR ARSE I DO! Yippee!!

Mike,
You really need to get your computer fixed up properly, I think Steve Mac is a pretty good computer guy so you may run your stuff by him.

Atta boy Steve! Shasta is a heck of a place to get excited about!

i nearly read this thread three times, both entertaining and interesting. thank you for getting the thinker going!