I see a few boats with the light mounted to the top of the motor cowling, they never have to remove it or fool with it. Is this legal, as far as height etc.... ??

It is legal as long as it meets several criteria:

1) Is an approved lamp assembly with sufficient color(white) and intensity
2) Is at least 39 inches above the red/green navigation lights (sidelights)
3) Is always visible from 360 degrees of view. This basically means that it must be the tallest thing on the boat (no matter where or how it is mounted). Keep in mind that shallow water anchors are NOT allowed to block the view of the stern light - that can get you a citation, or cause another boat not to realize your presences or headway.

Some people who buy a boat factory rigged with shallow water anchors have wondered why it came with such a long pole for the stern light. The necessity to clear those shallow water anchors (obstructions blocking view) prompts the factory to include a taller pole to avoid liability.

Some larger boats use two white lights to accomplish the all-around white light requirement, but I've never seen a bass boat take this approach. Each of the two lights is less than 360 degrees, but combined they provide a continuous view of a white light from any angle. At least one of those would still need to be taller than obstructions such as shallow water anchors.

Boats without taller obstructions may be legit with a certified all-around white lamp mounted to the top of the outboard cowling. I've seen some with a short fold-down light that worked, but may not have met the 39 inch height rule. Those boats didn't have shallow water anchors or center consoles, so most game wardens would probably never write a citation over the 39 inch height requirement.