This article shows you how to make a water pump boat that you see in the video. The water pump sucks in water that flows through a rubber hose to the back of the boat and provides trust (from pumped water) that moves the boat forward. The main advantage is that the motor propeller is covered inside the pump and would interfere with underwater wildlife or plants.

The old water pump was used to pump water to the front car windscreens. There are many different ways of making a boat from the old car water pump. You can use packaging foam or connect plastic bottles together with ropes or sticky tape.

Initially, I used a single 1 cm thick wooden panel. However, my boat was not floating and sinking due to the weight of the motor and batteries. Then I added another 1 cm thick wooden panel and I am not sure if the second 1 cm thick wooden panel was sufficient but I did not have any more left. You can see in the video that the boat is floating but batteries are slightly submerged in water.

I used a 3 V rated DC motor to save money. Thus even the 4.5 V source was too much to this motor. However, the motor did not fail even when I connected the 9 V battery. It must have been the high internal resistance of the 9 V battery that reduced the potential voltage across the 3 V DC motor and prevented motor failure. The water pump is supposed to be driven by a 12 V motor because 12 V is the car battery voltage.

Supplies

Components: 4.5 V, 6 V or 12 V DC motor, power source (3 AA/AAA batteries or 9 V battery), a thick metal wire (insulated or non-insulated - 2 mm), wooden panels/foam packaging materials, insulated wire, old water pump from a car, screws, sticky tape (masking, clear or cloth), plasticine/blue tack, wire holder (to attach the pump hose to the boat), 9 V battery harness (if you are using 9 V battery).

Tools: pliers, screwdriver, saw.

Optional parts: bolts, nuts, washers, battery harness, rubber bands, ropes, plastic bottles, battery harness (for three AA/AAA batteries).

Optional tools: soldering iron, wire stripper, drill (manual or electric).

Step 1: Make Fixture

I made this fixture with my hands and pliers. It is used to attach the motor to the boat.

Step 2: Attach Fixture

I attached the fixture with screws and washers. I did not use my electric drill this time. Drilling the holes before inserting the screws will prevent cracking of the thin wooden panel that I used.

Step 3: Attach Motor

I used a packing wire from a packaged loaf of bread. You can use metal wire, rubber bands or ropes.

Do not use sticky tape for this. The motor needs to properly attached to the metal wire fixture.

Step 4: Attach Water Pump

I attached the water pump hose with a plastic wire holder. You can create a metal wire fixture to hold the water pump hose. If your boat is made from plastic bottles or packing foam then unlike with the DC motor, you can try attaching the hose with sticky tape.

Step 5: Testing

Initially the shaft was not spinning (even with 9 V battery). I tried moving the motor slightly to improve the motor shaft alignment.

You can see in the video that even the 4.5 V source (although higher than the DC motor 3 V rating) is not enough to power the 3 V motor and make the boat move at sufficient speed. Yet the motor shaft is still rotating and the boat is moving.

I tried reversing the polarity of the motor power supply to see if the boat would move backward. This did not work because this particular pump was not designed to work in reverse.