Tandum axle trailer w/ 3500# axles gives you 7000# GVWR. The trailer will weigh about 800# if aluminum. So that gives you 6200# max for boat and motor + fuel and gear.
You probably weigh out something like this:
Dry Hull only 2800#
I/o w/ outdrive 1200#
fuel 100gal x 7 lbs/gallon = 700#
Misc gear & junk = 600#
Total boat on trailer = 5300-5500
so add the trailer back in at 800#
and you are towing about 6,200 lbs well within the safety capacity of a std tandum axle (7000 GVWR) trailer.
Here's mine:
I've got an outboard (Saves weight) but a tower too (600#) so we weigh out about the same. My trailer is just about perfect for my boat, tows like a dream.