I am planning to use 2 MFA 280 size brushed motors for my RC conversion of the Amati Titanic. The motors run on 12-24v with a speed of 8,400 rpm at 12 v. Next size up in the MFA range is a 360 size motor which runs on 6-15v with a speed of 8,320 rpm at 12v. Go up to the 380, and ir runs on 3-7.2 v, with a maximum speed of 19,000 rpm at 7.2 v.

I am using the 280 size because that is recommended in the conversion instructions and space is tight. However, I would like to understand why the smaller the motor, the higher the voltage required and what does it tell me about the power of the motor under load?

I will be using two 6v SLA's in series to produce 12v, these batteries chosen because they will fit in the hull. The rest of the electronics will be Mtronics Marine 10 ESC's and a Mtronics W tail micro mixer (this model enabling the rudder to be controlled along with the mix in motor speeds). Space is at a premium and these units seem an OK match to the motors running on 12v. Will I be OK with these.

Just a word of appreciation for the almost instant replies I get when posing questions on Model Boat forums. It is nice to know that there are so many experienced modellers willing to advise those of us less long in the tooth (in modelling terms, of course).