Fan on Motor, Speedo or Both?

[RC-Monster Mike]

The 18.97 with a 10L may not even need a fan most of the time, but it is always a good idea. Mount the fan so it blows air over the heatsinks (down or through doesn't matter, as long as it blows the air onto the heatsink) and you will be perfectly fine. Here is another tip-the heatsink fins onm my clamp will accept a 2mm threaded screw between them, so you could mount a fan to the heatsink using these screws to hold it in place.
165 degrees is not terribly warm for a hot summer day on a race track, either.