Slow IPSec Connection

[Tenou]

Hey there,
I'm using IPSec Tunnels to connect multiple remote locations to my main network.
Unfortunatly, the speeds I'm getting are really low. My internet connection is 100Mbit/s down and 45Mbit/s up.
For my remote location it's 400Mbit/s down and 45Mbit/s up. So it should be possible to get a file transfer to speeds of around 40Mbit/s.
Unfortunatly, in reality it's 5-8Mbit/s. Connection locally to the nas results in speeds of >10Gbit/s, so the NAS shouldn't be the problem ;)
CPU & RAM utilization is also very low, at around 1-10% for both.

Phase 1 config:
IKEv1
Proposal: AES256, SHA1, DH14.

Phase 2 config:
ESP
AES256
SH1, PFS14

Are the slow speeds results of the (really not great) configuration? I unfortunatly can't change that because of compatibility limitations. Would just love to try everything else before buying a new router.

[Derelict]

What kind of transfer? What is the latency across the tunnel? How exactly are you measuring throughput?

AESGCM will generally be faster overall than AES. Change the Phase 2 to AESGCM without a hash.