hi ya Colin, sorry for the delay - but I am going to open up a can of worms here. Although a lot of people use the 'Y' tail or the 'W' tail mixer from MTroniks or other Companies to actually mix two speed controllers and a rudder movement in the marine environment, (personally) I don't think this is effective as a dedicated marine mixer. The reason for this, is, I built the Forceful tug a little while ago and I incorporated the 'W' tail mixer in it for independent control of the 2 paddles and the rudder and when this model did 'sea trials' 😊 on the lake & in the test tank (the bath) 👍I was never 100% happy with this. it didn't seem to perform quite right, especially in reverse. The model seemed to go better in one direction than the other. One motor always seemed to lead the other motor so therefore the model would steer off course and you were always correcting it. When I eventually checked the speed of each motor individually with a tachometer I found that one motor was indeed increasing in revs so - I took out the 'W' mixer and went for tank steering (using 2 individual sticks on the transmitter). This was a lot better and saved the day at the lake. Then I wend and had a look at what mixers are available and yes there is the ACTion P94 which in my eyes is extremely expensive - but - there are one or two on Ebay market but also there is a guy called Alan Bond he runs a company called Forge Electronics and they make an independent mixer which I use myself. I find it extremely good. 👍
the name of the game though is for yourself to try setting up the 'W' tail mixer and playing around with it or you could look at individual mixers that do not have the speed controllers built in with them i.e. there is one from ACTion as well, there is one from Forge and as I say there are 2 or 3 off the web market place.
Have a look - here are a couple of pics of the Forceful and my set up. The speed controllers I am using in this tug are Electronize and it's Alan Bond's original mixer which used to be sold from Technobots - but he opened up business on his own and I will put a link on when I find it.
http://www.forge-electronics.co.uk/
http://www.forge-electronics.co.uk/