engine cooling question

we recently body dropped my 91 fullsize and naturally had to remove the mechanical fan from the water pump pulley.
i have an electric fan now installed and i think maybe it isnt pulling the cfm needed to cool this thing.
does anyone else out there with a fullsize run elec fans and have trouble?
do i need a dual fan setup?
what thermostats are being used?
thanks

WHAT ENGINE SIZE? i SWAPPED MY  92 WITH A 350 TO ELEC. FANS AND NEVER REALLY HAD AND PROBLEMS. HOW MANY WIRES ARE COMING OUT OF THE FAN MOTOR? THE THERMOSTAT I USED WAS FROM THE LOCAL PARTS STORE, IT WAS ABOUT $20.00 AND WAS ADJUSTABLE. WORKED PERFECT. BY THE WAY IS THE FAN PULLING OR PUSHING AIR, THAT WILL MAKE A HUGE DIFFERENCE? LET ME KNOW IF THIS HELPS. 

with it being in a fullsize, i'm sure you got room for 2 fans. since you are from the south, do you need heat? wouldn't you only need the thermostat if you had heat? i just wired up 2 fans on my bodydropped sonoma. they are 10" fans and were $45 with shipping off ebay. they are each 2-wire fans. and you can wire them up as pushers or pullers.

I am using 1 Ford Taurus cooling fan and it turns on for maybe 30-45 seconds idling through rush hour traffic.  

i have just 1 12" fan on my fullsize and it does fine. it did have some slight issues but switched it from pull to push and it does great

thanks for all the responses.the engine is a 350..sorry for not specifyingdid yall have to eliminate your overflow tank?i have a very small billet can on mine now and when she gets hot the boiling water just pushes through and out of the overflow tank.and i think that may be where the problem of over heating is originating from b/c im losing coolant .. but the question remains why is it gettting hot enough to boil the water out of the catch can in the first place?

check the level of the water in  the overflow tank and it is filled to much then when your engine gets hot itll spill water back into the overflow bottle.  If the bottle is to full it will spillout.    As for the question for the thermostat i would think that you would need one because  it regulates on temp. If your dont have then it is constantly running fluid through your motor and the motor will not get a chance to cool down. possibly blowing a head or water pump just a few examples

Are you using the stock overflow tank? Where is the tank located(stock loc. or relocated).

I had that same issue with a aftermarket overflow bottle, I had to find a spot for my stock one which is on my fender on the drivers side now

yea the overflow bottle is mounted right next next to the radiator by the cap.im sure i tossed the stock overflow a while back but im sure i can find one on ebay or at lmc