I think the rule of thumb for tongue weight is about 10% of the total trailer/boat weight. The tongue does look a bit short for that much of a boat. As sprink said it might be time to stretch the tongue. Here is my 8000lb scarab and I have right aroud 800lbs of tongue weight, notice how long the tongue is!

Toss some weight in the nose of your boat and recheck. A lot
faster and cheaper than to start throwing money into modifying your trailer hoping to find the issue

Take it to a truck stop with truck scales. In 15 minutes you'll know the tongue weight and no longer have to guess.

Run the whole rig on the scales, get the steering, drive, and trailer axles weights. Then drop the trailer and weight the two truck axles.

figure out the steering axle weight difference, and subtract that from the drive axle difference to determine the trailer tongue weight.

It's good knowledge to have.

Actually the trailer shop does have a scale, and we are going to do that as soon as i go back there in about 2 weeks , he told me if i move the boat forward 1 foot i will gain 300 lbs of tongue, but i don't think a foot will be enough.

I would think 2 axles would be plenty Diego. I bought my trailer and its gonna get Kodak disc with eoh. My truck is already set up for the electric brakes so I will just need the actuator. Like others have said must be air in the system or surge not working properly.

This will be interesting to find out. I find it hard to believe tongue weight is the problem. If you are stopping hard enough that your boat is lifting the rear of the truck up, the boat HAS to be pushing the trailer into the truck, thus applying the trailer brakes. But if it really lifting the truck up, you'd think the trailer brakes are not working correctly

I don't see where you checked the master cylinder for to orifice. Did you?

Also didn't see the answer if you can back up with the trailer plug unhooked.

I have not done it yet since I have the boat at my mechanic waiting for a 2 set of risers , once I get it out of there( in about a week) I will bring it to the shop and get this done.

My mechanic said he tried to back it up with the forklift and the brakes would stop it. so thy have a part the put in the trailer pump to release the brakes.