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How does IntelliJet achieve fuel savings?

  What about Rocks?

How does IntelliJet achieve fuel savings?


Propeller boats waste a lot of fuel and much of this waste can be eliminated.  In brief, IntelliJet does three things better than propellers: 1) it operates the motor more efficiently, so the motor delivers more shaft power for the fuel it consumes; and 2) it controls the flow of water through the propeller, so the propeller converts more shaft power into hydraulic power; and 3) it minimizes the velocity of the discharge jet, so that it produces more thrust force from a given hydraulic power.

1)  In a common propeller or jet boat the motor only operates at peak efficiency close to full power. At lower speeds, the power demanded by the propeller is well below the power that would be most efficiently supplied by the motor.  This would be unthinkable in your car, like driving down the freeway in second gear.  Imagine what that would do to your gas mileage and to your motor life. Thatís just what happens in most boats, but not in an IntelliJet boat.

2)  A fixed propeller of conventional jets is relatively efficient only in a narrow range of operating speeds and loads.  In fact, some people commonly change propellers for carrying different loads or running at different speeds.  Larger boats and ships like US Coast Guard Cutters use controllable pitch propellers to operate more efficiently over a wider range of speeds and loads.



 Jets have a reputation for using more fuel, because they cannot easily be changed, and are particularly inefficient away from their ideal speed and boat load.  IntelliJet addresses all of these efficiency issues by using a controllable pitch propeller pump, a controllable nozzle to vary the jet size, and a controllable inlet to efficiently deliver the required flow to the propeller.

 3)  At very low speeds, if the jet velocity is reduced by 50%, the thrust is doubled for any given hydraulic power. If the motor and pump efficiencies are constant, the same amount of fuel is required to produce a given amount of hydraulic power, so fuel consumption is reduced by 50% in the lower jet velocity.

The IntelliJet is controlled by a computer to realize all of these savings over a wide range of boat speeds and loads, and they add up to significant savings. 

You will find technical papers on the IntelliJet Links page that address these issues in more detail. 


  What About Rocks?      

The same design features that protect people from contact with the propeller also protect the propeller from damage related to contact with rocks and logs.  The hull must be pressed flat against the bottom to provide a means of sucking up rocks, and who wants to hear rocks scratching along the bottom of an expensive boat?  Even then, a rock the size of a tennis ball will pass through the system without binding.  The system will be equipped with a grate to prevent the larger pieces from getting in there in any event.

There is a greater probability of getting a waterlogged piece of wood into the system. If such debris causes a bind between the propeller blade and the stator vanes, the return spring in the actuator will act to relieve it, and the computer can detect the consequent hydraulic pressure drop pressure to sound an alarm.  It will be a rare piece of waterlogged wood that will have the ideal size, shape and strength to slip through the inlet grate and damage the pump, although it will no doubt happen on rare occasions. 

If the system sustains damage, it can be quickly fixed and returned to service.  The pump module weighs less than 100# and is a convenient size and shape to be exchanged by UPS.  It can be exchanged on the boat by the boat owner in probably less than an hour.  (See IntelliJET Modular Replacement video on home page under "How It Works".) This module contains most of the precision fits in the system, as it includes the tapered roller bearings, shaft, actuator, and pump propeller.  Any damage that would result from getting a log into the system would be likely to occur in this module.

The nozzle module is above the bottom of the hull and in the path swept by the hull in forward motion.  The only way to damage it is blunt force trauma resulting from backing the boat into the shore.  It will generally be protected from contact with the dock by the swim platform above it, so the swim platform will sustain damage before the nozzle does.  The nozzle module will also ship by UPS and can be replaced by the owner in about 15 minutes. 


It is easy to see that this beats any propeller system for prevention of damage, ease of repair, and minimum down time. 

There is a surprising perceptual problem related to jets, even though they are considered extremely durable in the aluminum jet river boats used in the West, where many boats havenít had an incident in years of operation in rocky river bottoms.  It turns out that teenagers on jet skis are a different story: the thrill of gunning it in shallow water is too great to resist.  Many people have had bad experiences with the consequences of rocks getting into their personal water craft that they wonder if the IntelliJet will suffer similar problems. In fact, PWCs are not designed for operating in the shallows and the resulting damage is not covered in their warrantee. Looking at the four-figure bill just makes the owner mad and that anger is transferred to all jets.  Again, the IntelliJet will pass rocks and branches that would jam and break the impeller of the much smaller PWC jet.

When the boat is in forward motion, the hull sweeps debris off to the side out of the way and also knocks floating debris down out of the suction path of the inlet of any jet.  Many jet boat manufacturers do not recommend the use of an inlet grate, pointing out that it creates a loss of power that makes the installation less efficient, so that the value of the fuel consumed is far greater than the risk of damage from anything getting into the jet. 



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