amp temp

I have installed a JL Audio A1400 in my vehicle.  It's mounted under the passenger seat, but has almost 3 inches above it for clearance.  The front and back of the unit is exposed so there is plenty of air getting to the amp.  I use the amp as a demo amp in my vehicle so that I can show my customers different boxes and how they sound in an actual vehicle not just the show room.  I run an Eclipse CD3200, with 5v pre-outs.  The gain on the amp is set to minimum.  There is a switch for High or Low signal input, I have it set for Low.

The other day I had two MTX 12" X-thunder subs, 4ohm each, wiring in parallel, 750watts max each, in a ported box in the vehicle.  I ran them super hard for about an hour.  I had crazy bass coming from these cheap MTX subs.  Afterwards, the amp temp was almost cooler than when I get in the vehicle in the morning.  There was no feelable difference in temperature.

Now, I installed the same amplifier in a ski boat.  The amp was mounted almost verticle.  Clarion head-unit with 2.2v pre-outs.  The amp runs two JL Marine 10's 4ohms, wired in parallel, in a sealed enclosure.  The amp is in a very open location.  This amp however, gets hot to the touch after only 15 to 20 minutes of running.  Gain is set to 1/2.  What gives?  do I have a magical amp in my vehicle?