A while back (several years ago) I was breaking in an engine on the lake tied to a dock, I was kneeling alongside the engine running the throttle by hand on the carb. and was not really paying attention to my surroundings, I looked up and me, the boat and the dock I was tied to was about 100 Yards off shore (whoops), so what ever you tie the boat to, make sure its up to the task...

GT

A pump dyno currently is a waist of time.  The video could very easilly show a pump with massive clearences but with a nice weight balance.  We did a dynamic balance like that thirty five years ago. Not much to gain.  What you don't know is how well each individual blade of the impeller matches the others. Is the bite exactly equal, is the front side and back side cup exactly equal, are the blade cords equal, any of these things will scew up the ballace when loaded. Then you throw in the dynamics of water flow through the pump in a moving boat and there are more variables than can not be computed at this time.  Issues like how much cavitation comes off the loader, or even the bolts of the loader? does water break off the gap between the suction piece and the impeller? Is there cavitation on the back side of the loader ramps? Is there any problem with the shoe, too deep, too shallow? Lord knows what problems an inducer could create with flow while increasing the intake preshure on the front of the impeler.  God the variables haven't barley been touched in jet design. If you wanted to develop a dyno for a pump I guess it would take preshure indicaters, slo-mo cameras, and an 800 hp electric motor. Then mount the pump upside down under a large swimming pool and then you could get an idea of what goes on after the intake, that's all.  Gooood luck!

Hey Stevecat, I think we're on to something here There seems to be a common denominator, guess I better keep my eyes open for a good used motor and VFD???

GT

Yeah find us a cheap 500HP with VFD, then about 800 ft^2 facility with a BIG main breaker panel, good water and a floor drain. And I think we need a 2.5:1 speed increaser with good quality gears. 

I called 10 places around the US and even called the US office of Hamilton. They all said they don't have a pump dyno. American Turbine has an impeller dyno. So they can tell you how much shaft power an impeller absorbs - which is very important of course... but it is not the same as inside a bowl and with water getting sucked, rammed and who knows what else up the intake, through the impeller across the wear ring over the stator vanes down the throat and blah blah.

Now I may have been getting sandbagged by some of them that I called but I tend to think not. A real pump dyno that could properly deal with the flow rates of a pump and then recondition the water and get the air out of it and back into the inlet at simulated hull speeds of 100mph would be big, expensive and very tedious to operate. And we would have heard about it. There are of course some very large and fast water tunnels in the US.  But these are usually academic/government operated and not rigged to do jetboat pumps all day long.

Jack at MPD told me what he was told of the story of how the Berk company developed their pump and they most certainly did NOT have much in the way of test equipment. They were doing what we do now - use the assmometer.

So the most fascinating thing for me about all this is that it would appear that nobody really knows whether a jetboat pump is 50% efficient, 75% efficient or 99% efficient (at converting engine shaft hp into thrust hp).

PS  - I've got $1 that says they are not 99% efficient!