Classic 1000 HOB skimmer limo

I installed a new classic 1000 hob skimmer about 4 days ago and there were several problems with the pump and connections. Both connections to the skimmer leaked, even with the O rings installed. I was able to fix that problem by using some silicone sealant. Not a good start.

Now there seems to be a problem with the pump. There is never enough water in the body itself, the water level constantly drops below the level of the output pipe, unless I fill it several times a day. There also don’t seem to be enough bubbles for skimming to really start.

Removing the silencer, it doesn’t sound like it should. There is a sort of thumping sound coming from the air intake.

The intake is right at the waterline with most of the cup in the water, with a bit of grating above the surface.

Please help with this.