you may already have an hin if you are documented. uscg does that. check your document.
if you have none in reality, send the copy of backside of document to uscg as a request for hin. mebbe can be done online--i do not know.
your boat was constructed in 1990, there should be a hin on record
with uscg--let them find it for ye. be legal
uscg will give you a proper hin. is only one that is official. they love official stuff here.
there is a place in bottom of my hold wherein lies quadrant. is out of the way and found upon good search. mine has document number on it.
if you have a builders placque, the hin is on that. if someone took that placque for a souvenir of their long lost
boat, you have no record
of this, although there was at one time a number. that number may have been recorded, so it is good to see if you can retrieve it from uscg. they have archives
so, your best idea is to have uscg make you a number and/or search for old one compared to (cross referenced) document number--these items are researchable when you google
your document number.
all records are there in that uscg info file. have you looked there for any other numbers than document number??
you may find it there.. good luck.
btw--it is different towing into mexico a boat than it is to sail it into mexico. you will learn this when you bring a large non trailerable into mexico. with trailerable, we found the inspector desired ALL numbers to MATCH-- boat, truck and trailer. this was in 2004. somehow the owner made all numbers match which appeased the inspector. no mordida.
as mordida is currently allegedly illegal, things may be easier., this is within a few short years in age.. is different under this president than last one.