Brushed thrusters

[UnknownROV]

Hi! I'm new in here and I have few questions which contains to thrusters and especially to the motors. At first I have to say sorry about my bad English but I hope you guys understand me.

I'm going to make ROV by myself with really control so I'll use brushed motors. I have already water-sealed old drill motor and tested it with computer cooler fan propeller. While testing I found out that motor took 1.5A when I run it without prop. When I add the propeller took motor about 5A in the air and 10A in the water while I'm running them with 12V. The biggest problem is that relays max ampere is 5A. I know that the shape of the propeller is far too aggressive and I'll buy new propellers as fast as I can. How ever here is a photo of my thruster:


So the question is does anybody know any good (and cheap and powerful enough) brushed motors and propellers for the thrusters? Motors must take under 5A when you are running them underwater with 12V. Hope that someone can help me whit this problem.

[UnknownROV]

I have browsed eBay and here is two candidates: one which spins 5000 rpm *click* and another which spins 10 000 rpm*click*. I already ordered two sets of 3 blade propellers whose size is 47mm, 52mm, 55mm and 57mm and pitch is about 35mm. Now I'm wondering can those motors run for example 52mm propeller how well in water and which one of motors are better 5k rpm or 10k rpm? I'd be happy if somebody could help me with this. Almost everything else is pretty clear at the moment but the motors perplex me.

[scubersteve]

The 5000 rpm motor would be the one to use. The amperage it draws will depend on the propeller you put on it.
I would experiment with different props to see which one gives you the most thrust while keeping the draw under 5 amps.

or you could just use bilge pump motors...

[UnknownROV]

Okay so I order few 5000 rpm motors. Thanks for that. I know that converted bilge pumps would be better and easier solution but they will cost at least three times more than those motors I have looked. My rc truck and tractor hobby takes so much money that I want to try to do this one by the cheapest way. But as everyone knows, once you get into something cool and exciting you just want it more and more and more.. But anyway thanks for advice and lets see how it gonna work.