Using a propeller to excavate sand under a boat

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SUMMARY

Using a boat's propeller to excavate sand is feasible, particularly when employing a tube to direct thrust downward. While some dredges utilize separate propellers, it is possible to use the boat's propulsion system for limited sand removal, specifically 1-2 feet of silt directly beneath the vessel. However, significant power is required for larger volumes of sand, and care must be taken to avoid clogging the engine's cooling water intake with sand and water mixtures. Additionally, considerations regarding propeller erosion due to sand exposure are crucial.

PREREQUISITES
  • Understanding of marine propulsion systems
  • Knowledge of dredging techniques
  • Familiarity with scuba diving operations
  • Awareness of engine cooling systems and their maintenance
NEXT STEPS
  • Research the design and operation of marine dredging equipment
  • Explore techniques for effective sand removal using underwater hoses
  • Investigate the impact of sediment on propeller performance and longevity
  • Learn about the maintenance of engine cooling systems in sandy environments
USEFUL FOR

Marine engineers, boat operators, scuba divers, and anyone involved in underwater excavation or maintenance activities.

Garry
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Good day. I want to use the boat's propeller to excavate sand. This will be done using a tube which will deflect the thrust downward. What are the implications? The boat is anchored. Thus there is zero forward speed. I suspect this may change the properties of the way the propeller functions.
All advice is greatly appreciated
 
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Yes you can do that. Some dredges do similar things, such as in this picture. But dredges normally use a separate propeller, not the ship's propulsion propeller.

dredge.jpg
However,
  1. Don't get overly ambitious. Moving lots of sand takes lots of power. But if you are just trying to remove 1-2 feet of silt directly under your boat, using a hose powered by your prop, and you in scuba gear to direct the hose, it can work.
  2. Consider how far away you move the sand. Too close and it will silt in again in a short time.
 
I think the treasure hunters already do this.
86ff3b1561641e61ce2b80df738c6393.jpg
 
Just keep in mind the location of your engine's cooling water intake and make sure you will not be ingesting any of the resulting sand/water mix into your cooling system.
 
I wonder how fast the prop blades are eroded? Perhaps there is a way to avoid sand going through the prop.
 

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