My Aquarama is not overly fast with these motors, it runs scale speeds at about 3/4 throttle with 29mm three blade props.
They are only 28mm diameter motors remember so they don't produce as much grunt/power as your bigger can size motors.
I chose these smaller size motors because:
1. The bigger the diameter of motor, the further forward in the boat you have to mount it to achieve the correct propshaft angle. I couldn't install the motors any further forward or lower in my hull so my choice was limited.
2. Price. I couldn't find the Leopard 4064 1050KV but the Turnigy AquaStar 4084-1050KV Water Cooled motors are £46 each!
http://www.hobbyking.co.uk/hobbyking/store/__31677__Turnigy_AquaStar_4084_1050KV_Water_Cooled_Brushless_Motor.html3. Price! again!
4. Motors like the Turnigy D3548/6 790KV are fine but its an outrunner and you obviously can't add a water cooling jacket to it. You can buy motor mounts with water cooling but there's not many options and they are quite pricey.
5. To achieve the correct RPM for your boat to get up and plane with a lower kv motor, you might have to use a higher voltage lipo, maybe a 4, 5 or 6 cell.
I already had lots of 3S packs and didn't want to invest in new ones so I over estimated the kv needed to make sure it would get up and go.
Having said all of this, if I could build this boat again, I would go for a single Turnigy AquaStar 4084-1050kv, 100amp ESC and 4S lipos with at least 5000mah capacity with should give you about 30 minutes run time and a single rudder.
Installing twin motors and rudders is a bit of a pain really, it's twice as much work for not that much gain IMO. It looks great and all of that but you can't see them when it's on the water so...