100 hp centrifugal jet pump design help

I lost some of my video lending it out, very important stuff.Take a look at the new centrifugal type outboard jets.Arnold France I understand did the initial development work for Hamilton but fell out with the company over different issues. like all inventions jets are a combined effort of many people trying different ideas.
Apparently it was a farm hand who suggested that the expelled water should be expelled into the lighter atmospheric pressure thus (like surface drive) efficiency improved.

 

The stream of water coming out of a jet does exit into atmospheric pressure. If it were to exit into water, the thrust would be lower.

If you do not believe me, take a garden hose and put it on the jet position, high speed, and point the nozzle down
grab the hose as far back as you can so the thrust of the water is holding up the portion of the hose and nozzle in the air, ie thrust equals the weight of the hose and nozzle ( prox of course)
Then drop the nozzle into a buck of water, the minute the jet of water gets close to the water, the hose and nozzle will drop into the bucket. ie less thrust

 

Tom
I could did not find any info on another outboard jet except the pumps manufactured by Outboard Jet a division of Specialty Marine in NW USA
While the pump external profile looks similar to a centrifugal pump it is actually a mixed flow pump that needs this shape to get the thrust parallel to the centerline of the boat. I have owned 3 of these pumps and they work well

 

I don`t think anyone has disputed what you say here. The principle seems to be well known.

 

Try Yamaha outboard 4 stroke jet.com

 

What is missing in this discussion is the design speed of the vessel. That is a significant factor in the selection of the "optimal" type pump. Some of the USNavy hydrofoils used centrifugal pumps. Certainly there are other considerations in that application regarding vertical rise in the inlet to outlet.

Also, if the size of the pump is a factor, it might change the selection. As always, making the proper tradeoff of is the key to a successful application or a flop.

As for the previous discussion of the White-Gill Omni thrusters; I believe that they all were vertical shaft axial impellers with a very convoluted inlet to outlet path. It does make for a nice compact package and in some cases is an excellent solution, but certainly not a very efficient one.

 

Hi Tom
The Yamaha pump is a mixed flow pump made by Outboard Jet, as is Merc, etc


Johneck
I was not aware that the navy used a centrifugal pump on their hydrofoil jet powered boats. With a larger vessel, filtering the debris out would be an easier possibility than in a 20 foot personal jet craft. As they do not have to pay for the inefficiency, the tax payer does, they probably do not factor in running costs.
Any links to the type of pump they use.

 

We used hundreds of different types of pumps in the dairy industry the centrifugal standard pattern used mostly and their big problem was self priming at which they were very bad and needed a good head of fluid to start pumping.
The same problem would apply to boat propulsion.
Yamaha jet pump image.
www.gobookee.org/jet-pump-on-yamaha-fx/ Axial flow pump

 

You may find this website interesting
www.duckworksmagazine.com/03/r/articles/jet/drive1.htm Experimenting with industrial centrifugal pump for a boat.