Bob. Unless ACtion do something to handle the expected 20A+ per pair of motors, and assuming by "F14stix" you mean pair of wagglers on your Tx set, then perhaps an Mtronics W-tail mixer might do combined with two 30 or 40A ESC.
This would mix the left and right motor pairs for manouverability and also give you an output for rudder?
OR simply getting a Y-lead for normal one stick throttle operation, controlling two speed controllers..to split the load. I am a bit wary of high power single ESc`s and their ability to dissipate heat, unless watercooled.
This is also a situation for one of those little watt-meters I found. Connect the motors up with shafts and so on, then simply try the pairs of motors in boat in the water with either just a battery across the leads or any handy esc of more than 30A capacity and measure the actual current consumption. So easy with one of these meters. Will give you more idea of the likely load and so equipment requirements and even the need for cooling.
Ashley