So I have an actor BP with a static mesh which is a boat and have a second static mesh which is a fishing rod with a hook which has a physics constraint. I also have a buoyancy component on the BP.
I’m a bit of a noob, but recently been doing buoyancy stuff. It looks like all your pontoons are in the same spot. they should be in the “corners” to give stability.
Check your Waterbody as well and make sure the collision preset is “waterbodyCollision”.
Then there’s the thing about the static mesh being the root. Look at the warning box below step 8. https://docs.unrealengine.com/5.2/en-US/water-buoyancy-component-in-unreal-engine/. I’m not sure why this is, or how to get around it. but i would try setting up an actor with just the boat and get that working first, then try to add stuff.
Increase the mass (alot). 10 kg is way too low for 4 pontoons with a radius of 100. try 100 kg or just increase it until it sinks, and then start tuning from there. The damping parameters on the boat might help too. But definately increase weight or lower pontoon radius until it seems to float, not bounce.