:triple axle venture, just put all new bushings , tires and aligned it...towing with a 2500hd duramax and like the title says ...she swings alot sometimes pretty big...im guessing maybe the wheel set needs to go back farther ?? hauling a scarab thunder w twin 454 aprox 8500lbs fyi i drive a semi for a living... thoughts ??

Sounds like its trying to tricycle on ya, maybe a little more tongue weight ??.......

I have the same problem with my 2014 Shorelander duel axle. I have been told the wheel set needs to move back. Tongue weight is the answer.

Tongue weight should be at least 5% of the total load weight.

Also the trailer should ride level front to back, use the right combination of tow bar to achieve the desired height.

Take your loaded rig to a scale and get us 2 weights:

1) Total of boat on scale which hitched to truck. (trailer axles on scale, truck completely off of scale)
2) Drop the tongue jack on the scale, and lift the weight of the trailer completely off the ball. (entire weight of your towed load)

If you want to go even further, get individual truck axle weights too, when hitched to the boat, and then leave the boat in the lot and go back with just the truck only.

Before you do any of the above, make sure you have a hitch drawbar that makes the trailer sit level. Check with a level on the trailer frame rail.

As mentioned, I too suspect you have too little tongue weight. You may be able to adjust my moving the boat on the trailer, or you may have to shift the axles.

Most concerning: what kind of trailer brakes do you have? If you have a surge brake coupler; this mis-balance of weight distribution is going to really make an emergency braking situation, sketchy, in a hurry; if not worse.

EoH is ALWAYS a smart upgrade (if you don't have it already), unless you are pulling a 20 Baja with a 1-ton. (facetiously speaking on that last part)

Typo? Surely you mean too LITTLE tongue weight.

You are right, thanks for pointing that out.

But too much or too little tongue weight will make for a terrible towing experience.

Too much provides lift on the front of the tow vehicle making it very hard to control, likely understeer.
Too little means you have tail wagging the dog, and the pendulum action of the trailer moves the truck all over the place, sometimes even lifting the rear axle of the tow vehicle.

thank you all...its good to see everyone agree this should be pretty easy to remedy

You need more hitch weight , how far down does the truck squat when you hook the boat? You also might need hitch anti sway bars.

Like everyone above says, sounds like a case of too little tongue weight to me. Somewhere I have a goofy tongue weight digram whe you can use a bathroom scale to measure it if you can estimate the total towed weight. 5-10% is the goal .