It's just what I asked I come from electric air and some reddy to run cars and need to learn about boat power systems why is so much amperege required and will any motor work if you get the kv in the right spot with a big enough speed control

There's WAY more drag in water, so it takes A LOT more power to push a boat the same speed as a car or plane.

Originally Posted by Looking_Up

It's just what I asked I come from electric air and some reddy to run cars and need to learn about boat power systems why is so much amperege required and will any motor work if you get the kv in the right spot with a big enough speed control

Start by working out what lipos you are going to use-3s/4s,etc,then make sure the motor can handle your lipo voltage,withthin the specs.Generally speaking you need 30000-35000 rpm,a sharpened and balanced prop,the bigger the prop,the amps are increased.Check your temps,of motor/esc/lipos after a 1 minute test run in the water,and if okay,move up to a slightly bigger prop,and check temps again.Theres also alot more to it as well,but thats a starting point.Make sure your esc,is at least 30-80 amps above the max amps of the motor specs,as you will get amp spikes.

look at other threads , look at what they are running and what size boat the power system is in . That way you will get a good sense for matching up motor , esc , battery packs , prop and other drive train components . If you have questions come back here . Theres always one willing to help . Also look at the better RTR boats , they make sure there boats are pretty fast and as reliable as possible .

I guess my question was more of a theoretical one as example with my little airboat it weighs 11.5 oz or 13.5 with a 2200 3s yet a 70 to 100 watt motor on a 12 amp speed control air cooled will put me at about 25 to 30 mph
However if I was to go with a water setup it would likely have to be 30 to 60 amp speed control and a motor probably 3 times as powerefull to reach the same speed all watercooled and heavier by half or more and I was just wondering if someone actually had a deeper answer than more drag when I am not shure that that statement is true due to my performance with substantially less power just delivered as air thrust over water thrust
I know I am oversimplifying but why can I not run the same noted and speed control but use a water prop and get the same results sa with the air prop

Your question makes sense but I would first ask if you are sure you’re getting 25-30mph out of the air prop? I would say you should be able to use a similar set up with a larger ESC to be safe and get equal if not better performance with a water prop. The water prop should be more efficient at producing thrust because if it wasn’t most all full scale boats would be air driven not water driven. My $.02 for what it is worth.