--- a/testing/marionette/client/marionette_driver/marionette.py
+++ b/testing/marionette/client/marionette_driver/marionette.py
@@ -539,20 +539,25 @@ class Alert(object):
         self.marionette._send_message("sendKeysToDialog", body)
 
 
 class Marionette(object):
     """Represents a Marionette connection to a browser or device."""
 
     CONTEXT_CHROME = "chrome"  # non-browser content: windows, dialogs, etc.
     CONTEXT_CONTENT = "content"  # browser content: iframes, divs, etc.
-    DEFAULT_SOCKET_TIMEOUT = 60
     DEFAULT_STARTUP_TIMEOUT = 120
     DEFAULT_SHUTDOWN_TIMEOUT = 65  # Firefox will kill hanging threads after 60s
 
+    # Bug 1336953 - Until we can remove the socket timeout parameter it has to be
+    # set a default value which is larger than the longest timeout as defined by the
+    # WebDriver spec. In that case its 300s for page load. Also add another minute
+    # so that slow builds have enough time to send the timeout error to the client.
+    DEFAULT_SOCKET_TIMEOUT = 360
+
     def __init__(self, host="localhost", port=2828, app=None, bin=None,
                  baseurl=None, socket_timeout=DEFAULT_SOCKET_TIMEOUT,
                  startup_timeout=None, **instance_args):
         """Construct a holder for the Marionette connection.
 
         Remember to call ``start_session`` in order to initiate the
         connection and start a Marionette session.
 

--- a/testing/marionette/harness/marionette_harness/runner/base.py
+++ b/testing/marionette/harness/marionette_harness/runner/base.py
@@ -235,17 +235,21 @@ class MarionetteTextTestRunner(Structure
 
     def run(self, test):
         result = super(MarionetteTextTestRunner, self).run(test)
         result.printLogs(test)
         return result
 
 
 class BaseMarionetteArguments(ArgumentParser):
-    socket_timeout_default = 60.0
+    # Bug 1336953 - Until we can remove the socket timeout parameter it has to be
+    # set a default value which is larger than the longest timeout as defined by the
+    # WebDriver spec. In that case its 300s for page load. Also add another minute
+    # so that slow builds have enough time to send the timeout error to the client.
+    socket_timeout_default = 360.0
 
     def __init__(self, **kwargs):
         ArgumentParser.__init__(self, **kwargs)
 
         def dir_path(path):
             path = os.path.abspath(os.path.expanduser(path))
             if not os.access(path, os.F_OK):
                 os.makedirs(path)
@@ -342,17 +346,18 @@ class BaseMarionetteArguments(ArgumentPa
                           default=False,
                           help='Enable the jsdebugger for marionette javascript.')
         self.add_argument('--pydebugger',
                           help='Enable python post-mortem debugger when a test fails.'
                                ' Pass in the debugger you want to use, eg pdb or ipdb.')
         self.add_argument('--socket-timeout',
                           type=float,
                           default=self.socket_timeout_default,
-                          help='Set the global timeout for marionette socket operations.')
+                          help='Set the global timeout for marionette socket operations.'
+                               ' Default: %(default)ss.')
         self.add_argument('--disable-e10s',
                           action='store_false',
                           dest='e10s',
                           default=True,
                           help='Disable e10s when running marionette tests.')
         self.add_argument('--tag',
                           action='append', dest='test_tags',
                           default=None,