scout.mpi: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/lib64/mpich/bin/scout.mpi - from package: scalasca-mpich
/usr/lib64/openmpi/bin/scout.mpi - from package: scalasca-openmpi

You may install the required package with command yum install {package}

Error in other languages:
scout.mpi: bevel nie gevind nie
scout.mpi: comandă negăsită
scout.mpi: comando não encontrado
scout.mpi: commande introuvable
scout.mpi: command not found
scout.mpi: käsku ei ole
scout.mpi: không tìm thấy lệnh
scout.mpi: komanda nerasta
scout.mpi: Kommando nicht gefunden.
scout.mpi: kommandot finns inte
scout.mpi: komut yok
scout.mpi: nie znaleziono polecenia
scout.mpi: níor aimsíodh an t-ordú
scout.mpi: no se encontró la orden
scout.mpi: no s'ha trobat l'ordre
scout.mpi: opdracht niet gevonden
scout.mpi: parancs nem található
scout.mpi: perintah tidak ditemukan
scout.mpi: príkaz nenájdený
scout.mpi: příkaz nenalezen
scout.mpi: команда не найдена
scout.mpi: командата не е открита
scout.mpi: 命令找不到
scout.mpi: コマンドが見つかりません