Thrusters: I am going to use Rule 1100 gph bilge pumps. These actually are pretty expensive but like I said on the home page it is simplicity over cost. Some people say the bilge pump replacement cartridges are cheaper but I found the price about the same for similar gph. I will use 50mm propellers because it seems that they are the best balance between amps and power. The shaft on the pump is suppose to be 1/8". The propeller uses a slightly larger 4mm screw. I used a 1/8" to 1/8" coupler and just drilled one side out to 4mm. I then grinded one side of the 4mm screw down to make a D shaft. Eazy breezy.
I did find cartridges that were cheaper than the full pump assembly. And I did not have to cut off the housing. Drilling out the coupler to 4 mm worked great. The 1¼, 4-way, pipe joint I used was a real tight fit for the cartridge so I used a rasp to loosen it up. I cut off the front and back "arms" because otherwise it was too long for the cartridge assembly. The cartridges came with two tabs. I cut one off and used the other one to hold the cartridge in place. I don't think it is necessary but just in case. 3" PVC was used as a propeller guard. There are a lot of wires going by the thruster in the middle so I created a housing out of aluminum to keep the wires away from the propeller.
There have been some comments about the bilge pumps not lasting very long. I cut the top off one to see what was inside. As you can the pump shaft has some grease-like stuff and a simple flat rubber disk that I imagine is used to keep water out. Remember, these pumps are not under pressure from water so normally it just has to keep out the water that it is pumping out. I put a bunch of vaseline jelly in the bottom of the case, reinserted the pump, then poured in wax. The idea was to have jelly keep out water and then the wax to prevent the jelly from displacing. The wax filled the entire housing including covering the pump. I left the other pumps like they were to see if what I did makes a difference. If you want to cut off a top also make sure you cut right at the top or you will hit the wires coming out of the motor. The jury is still out on this because the motor with the wax does not sound smooth like the others.
I did find cartridges that were cheaper than the full pump assembly. And I did not have to cut off the housing. Drilling out the coupler to 4 mm worked great. The 1¼, 4-way, pipe joint I used was a real tight fit for the cartridge so I used a rasp to loosen it up. I cut off the front and back "arms" because otherwise it was too long for the cartridge assembly. The cartridges came with two tabs. I cut one off and used the other one to hold the cartridge in place. I don't think it is necessary but just in case. 3" PVC was used as a propeller guard. There are a lot of wires going by the thruster in the middle so I created a housing out of aluminum to keep the wires away from the propeller.
There have been some comments about the bilge pumps not lasting very long. I cut the top off one to see what was inside. As you can the pump shaft has some grease-like stuff and a simple flat rubber disk that I imagine is used to keep water out. Remember, these pumps are not under pressure from water so normally it just has to keep out the water that it is pumping out. I put a bunch of vaseline jelly in the bottom of the case, reinserted the pump, then poured in wax. The idea was to have jelly keep out water and then the wax to prevent the jelly from displacing. The wax filled the entire housing including covering the pump. I left the other pumps like they were to see if what I did makes a difference. If you want to cut off a top also make sure you cut right at the top or you will hit the wires coming out of the motor. The jury is still out on this because the motor with the wax does not sound smooth like the others.