I have a fan mounted behind my motor on my 8-E-3.0 blowing out the rear. It is only a 30MM fan but by blowing air out from under the body it dropped my motor temp 10-15 degrees (it was already in a safe zone, about 170F after 10 minutes, but I figure the cooler the better). I have found that fans mounted vertically last much longer than those mounted horizontally. Also the thicker the fan is, the more robust they tend to be and you can frequently use a thicker fan mounted vertically than horizontally on top of the motor.