On Sat, 08 Dec 2007 09:01:49 -0500, Gene Kearns
wrote:

Anyway, for me, that would mean that the tow vehicle manufacturer's
GCVW rating should be in the 14,000# range to afford just a bit of
safety margin. Anything over the bare minimum will add usability,
comfort, longevity, and safety.

All of that is true but 14,000 GCVW is well over actual requirements.
I towed a comparable boat and two axle trailer over 1,400 miles,
Connecticut to Florida, with a V8 4WD Toyota Tundra. We had no issues
at all after the initial tuning of tongue weight and tire pressure.
The dealer set it up at 5% tongue weight but we found that stability
was greatly improved at closer to 10%. The Tundra is rated at 11,800
GCVW with the trailer towing package and off road suspension. Towing
65 to 70 mph with overdrive locked out, the 275 cid engine was turning
about 3200 RPM. Normal hills were not a problem and there were no
cooling or stability issues of any kind. Acceleration is noticably
slower than normal so you need to allow more distance when merging
with high speed traffic.

On Sat, 08 Dec 2007 11:25:16 -0500, Gene Kearns
wrote:

Truck 5500#
His Boat 5100# (dry)
Trailer 1700#
_____________

Yields 12300#

Junk and Fuel probably close to 1000#

What did I do wrong?

Nothing wrong using your numbers but my truck weighs about 5000
including rear cap and two passengers. By reducing junk and fuel a
bit more you are well within the ratings of a Tundra.