QUESTION1: How HOT does it really get INSIDE the cabin of a Cruising
Boat, in the Tropics? What's the typical you've experienced? What's
the worst-case??

I write this from my sailboat in Puerto Vallarta, MX, where we have
been all summer and the average temp is mid 90's every day.

My perspective is that every boat down here which has people on it
right now, has air conditioning. So my current interior temp is 74
degrees.

In December it will cool down into the 70's here, many boats and
people will come who don't have ac, but the temp is still in the 70's.

As someone mentioned above, the hottest time is when you are underway,
running your engine because there is no breeze (most of the time
here). But most of that heat goes right up the companion way.

Most people here have normal laptops, and they all work fine. I agree
that unless you are taking yours out into the cockpit where rain/salt/
sun can get to it, you should have no additional issues.

-Mark
http://GoReads.com