"It's unbelievable! Now, the question of a darker color meaning a higher temp inside the boat has become a matter of opinion!"
"As someone else mentioned when the boat is sitting in 85 degree water, the interior
is going to be about the same. Doesn't matter what color it is."
No logic necessary - just some thermal dynamics. Check out the links at the bottom of this message for actual experiments that confirm what I propose here. There are hundreds of such experiments posted on the web - not to mention many similar experiments I conducted in my physics classes
I think if you conducted a simple experiment
you would find the logic in the 2nd statement above in the specified situation: Very hot sunshine and very warm water where the thermal mass of the water far exceeds the thermal mass of the boats.
Let two similar sized boxes with thermocouples inside float, semi-submerged in 88 degree water in the Mexican sun for a week or so. One box is colored white and the other black. Start the test after the boxes have been afloat for several days and have reached thermal equilibrium with their marine environment
. The volume of the water would have to be many magnitudes greater than the volume of the boxes.
Each morning, as the sun rises and heats the boxes exteriors, the temperature rise in the white box would be less steep but later in the day both boxes will have an internal temperature that stabilizes at about the same temperature.
The lower internal temperature due to less energy absorption would be short term and not significant. Additionally, as the black hull heats it also radiates infrared energy more efficiently and since only the exterior is black it radiates that energy outward - back into the air.
Then, when the sun goes down the black box will radiate away the absorbed energy at a faster rate and thus it's internal temperature will drop more quickly after sunset. Eventually the internal temperatures of the two boxes will stabilize at approximately an equal temperature.
So - when you really want cooler internal temperatures, evenings and at bed-time, the black hull might be better.
Sure - a light colored deck and/or hull reflects sunlight or absorbs LESS infrared energy from the sun BUT in real life when both boats are soaking in very warm water the hull color makes little difference.
OR - maybe my empirical observations on dozens of boats over three summers in one of the hottest marine
environments in the world were in error.
Here is a link to an real life test - black and white automobile sitting side by side in 96 F sunshine - after 30 minutes of simultaneous testing the digital thermometer in each read the same.
Here is another link - a science fair project
that duplicated my proposed experiment
External color made no difference to internal temperature!