Is it possible - water jet drive with 5 hp engine?

Currently I'm building small boat and have stupid idea to equip it with 5 hp water jet propulsion. Can't use bigger engine now because in my country exist some rules with this.
I understand that I will lose half of the engine power by installing water jet drive, but I need waterjet because will sail in the shallow waters of the river. I also understand that I will have the water jet drive to create itself, because such small capacities there is nowhere suggested.
I need a boat speed of just about 15 km / h, but I think this is - a difficult task for 5 hp waterjet, and I hope that someone intelligent and motivated me to advise me not to do this way ...
But it will be difficult to persuade me, because on the internet I found the following two things:
First: Madly funny experiment with garden pump, which proves that the wiser use 5 HP can achieve 15 km / h with a small boat.
Second: Serious company is trying to create something similar.
And the third thing: I have already made their own boat hull. It was designed for the water jet drive.

 

It can be done, but you will need to build many parts yourself. There is a small boat made with a 7hp motor that can reach 24 km/h.

http://www.mokai.com/engineeringWide.html

 

There you go, it CAN be done.

$5000+US and it's yours!

 

If you are looking for maximum speed, a flat bottom boat is what you will need. However, you will need to keep the boat plus crew at not much more than 100Kg. About the links you posted: The first uses water from a hydrant. It has a lot more than 5HP produced. The second has no real technical information but just claims typical of a not too honest sales pitch. A propeller in a tunnel or pocket can be a cheaper and easier solution. Making your own impeller and duct is very difficult and expensive.

 

Just use any gasoline powered centrifugal pump, intended for agricultural purposes, pool cleaning etc.
Plenty of products here: http://www.waterpumpsdirect.com/pumps/gas-powered-water-pumps.html

All pumps create thrust, you just have to experiment with the nozzle size to get the best performance.

 

At first I was dubious, but after seeing this video - it's fantastic - 7hp

http://www.youtube.com/watch?v=OUilmqkvrLs

great

 

It's fantastic BUT - US$ 4800 is rather steep isn't it ??? (basic model)

 

I quite like Gonzo's idea of an enclosed prop as an economical allternative.

 

Flat bottom plus timber equals high boat weight. Anyway I believe you are very right about propeller in the pocket or tunnel. I must think how to adapt it for my boat. After all, anyway I can see, my boat's keel is too deep for useful water jet. Thank you.
P.S. Yelow hydrant was not used for jet propulsion. Was used water pump with 5.5 hp Briggs & Stratton Intek engine.

 

Squandered the The Cavalier Foundation for one motorized kayak, when a river navigation season lasts only four months a year? That what to do in the winter? To drink cheap wisky? No way Better will buy cedar planks for new kayak building. Interestingly, can I buy just propulsion unit from MOKAI...? It works perfect when I watching videos of them's. I even find the engine on a sale for it. Not SUBARU, but have almost similar parameters and cost not much. Genuine chinees product.

 

A 12' plywood skiff is about 100lbs (45kg) if built rather strong. How light are you aiming for?

 

Oh yes Like with 7 hp boat runs perfect. Imagine a cedar planked kayak with this water jet propulsion. No doubt will be chained with stainless steel bottom, but the boat would be a nicer without the plastic noise when water waving .

 

The boat hullboat hull I have almost built. Mahogany hull thickness is 6mm. It is very strong in all directions because have no flat faces. I'm trying to suggest that it is similar to weigh about 60 kg with all partitions. Will see...
Now I need knowing how to make the pocket for propeller.

 

The boat hull I have almost built. Mahogany hull thickness is 6mm. It is very strong in all directions because have no flat faces. I'm trying to suggest that it is similar to weigh about 60 kg with all partitions. Will see...
Now I need knowing how to make the pocket for propeller.

 

Not very much I understand hidrodynamics but I think centrifugal pump is designed for generating relatively high water pressure. For waterjet propulsion is needed not only presure, but is needed big water's volume. When small engine is generating high presure, can not push big volumes of water at the same.