Trailer tongue weight ?

[abl1111]

I have a 1975, 23' Tsunami w/ a 5.7 litre I/O w/ Bravo 3. 75 gallons of fuel and maybe 200 lbs of add'l gear-

My float-on, bunk trailer needs to be adjusted. It is a mid 80's, I-beam, Rocket trailer that has seen better days but works for what I need ( 2x a year )

It is a tandem rig w/ the ability to adjust axles forward or back. The rear tires seem over weighted, and she fishtales a bit - even though some crazy Floridians drove her up to me in NY a few years ago that way, I would not go more than the 2-3 miles I need to.

What is the tongue weight supposed to be, and how many inches back, roughly, will equate to the neccessary adjustment ?

Also, I need a supplier for a galvy, 2x4 trailer tongue - no one seems to have this odd size. It has to be 2x4.

Thx