akka remoting is fabulous for exchanging small messages. By default the maximum-frame-size is 128000 bytes and messages larger than that size are logged and dropped with akka.remote.OversizedPayloadException. You can tune maximum-frame-size but you should keep it small since remoting is used for core akka functionality such as cluster heartbeats. Larger messages will hog the channel and cause problems.
If you have larger messages you either need to break them down into smaller ones or look for an alternative protocol such as akka http or akka streams.
akka.remote.netty.tcp.maximum-frame-size
If you google for 'akka maximum-frame-size' you'll find more background.