Hi. What is your driver version?
I have 1060 3gb like yours. When i start zm. Hashrate is 310 sol. Then (after 1-2h) the hashrate will decrease to 260-270
Over 60° the cards start to throttle. Only 1-5 %. At 70° they throttle even more. Keep below 60° to get Full Power. Thats my experience with 3 setups with 1060 3/6GB, 1070TI and 1080TI.
And thats why your hashrate goes down after a while, cause VRMs/GPU and MEM is hot and the card slowy begin to throttle.
My setup after hours of mining:
ID DEVICE NAME °C ∅ Sol/s ∅ Sol/W ∅ Watt
0 GeForce GTX 1080 Ti 50 652.34 4.11 158.67
1 GeForce GTX 1060 3G 50 277.33 3.86 71.92
2 GeForce GTX 1070 Ti 52 491.61 4.58 107.23
3 GeForce GTX 1060 3G 49 274.56 3.83 71.74
4 GeForce GTX 1060 3G 54 274.18 3.82 71.71
5 GeForce GTX 1070 Ti 46 492.15 4.58 107.49
6 GeForce GTX 1060 3G 54 277.34 3.87 71.68
Total - 2739.51 4.09 660.44
The ambient temperature is 12° (thx winter)
Im using Win7 and the cards have these settings:
GTX 1060 3GB hynix: GPU +240 MEM +400 PL 60%
GTX 1070 TI : GPU +180 MEM +600 PL 60%
GTX 1080 TI : GPU +160 MEM -100 PL 60%
Theres a little room for stability. 1080 Ti runs since 1 year 24/7 with these settings without hassle. I prefer a rock stable system.
In a downtime you are losing money. So a little lower performance is okay for me.
If... If your cards are throttling at 60C it's because you dropped your powerlimit and didn't raise your temp threshold.
I got 1060 6GB with Hynix Ram doing doing 330-330 no problems. They run anywhere from 58-65C. I've had them near 70 too with the same results. The cards can do it you just have to make sure when you drop the powerlimit that you unlock it from the thermal threshold and set it to a reasonable temp.
GTX 1060 6GB hynix: GPU +250 MEM +400 PL 80%: 320-330H/sec :Temp 58-65C (2 different rigs reason why big temp flux)
My thermal limit is set to 75C currently but going to drop it to 70C when I switch out cases.