Onkyo & Outdoor Speaker Setup help

Sup everyone, first time poster here, I have a question I am told the people in the forums here will indeed have the knowledge to answer, which gives me confidence in asking.

I currently have an Onkyo HT-S580 which I use in my living room, 5.1 fully active using fiber optic. We recently purchased Yamaha NS-AW390 outdoor speakers.

As you can see, the Onkyo system has A/B speaker capability. Using the B speaker set, I hooked up the outdoor speakers securely and correctly, running them about 20-30 ft out my back door, using standard speaker wire.

The A speakers run fine, but the B speakers cause the system to enter the protective state, shutting it off. They can play at times but turning them up causes the system to shut off.

I am very good at hooking things up (inserting wires, cables), however I am not very good with specifications/electricity/current flow/ohms, etc. I took a rather poor approach assuming the speakers would work fine, but they are not, so I look to you guys for guidance.

Can anyone tell me what's up, and tell me what I should do?

Thanks in advance

Ok I see the link to the reciever I posted no longer works for whatever reason, to view it please visit here.

Seems like the receiver is designed for 8 ohm speakers, and these outdoors speakers are 6.

Is that the problem, and can I fix it without buying new speakers?

It does it either way, when A&B are on, or just B. I've checked the wiring multiple times, it seems fine...the copper from the wire may have gotten slightly rusty in the rain, could that make a difference? We've gotten an unusual amount of hard rainy days here.

No, the A speakers, hooked up only to the 5 speaker set and sub that came with the system, works perfectly, and has been for years...only when B is on, by itself, or in combination, does it shut off after about 10-30 seconds...