Single axle trailer guys. Need opinion

[tsubaki]

Correctly set up and correctly maintained it will be fine.
I still have the original trailer sold with mine in 1975, granted the only things original are the frame, axle, tongue and winch stand.

Just always keep in mind that you are going to be at the upper limits of capability of a 3500lb trailer.
Boat 1920lbs
60 gallons of fuel 480lbs
Engine +400lbs
You still need to make weight allowances for other things like batteries, coolers full of whatever, fishing gear, safety equipment, etc.
Depending on the manufacturers ratings you may need to take into consideration the actual weight of the trailer which will average over 500lbs.

Getting the tongue weight correctly proportioned is critical.

I'll eventually convert mine to a dual axle but that won't improve it's actual rating.