Yes, if you have a boat which hull is made from metal the MOB+ can still be used and will function as intended.
If you have a metal cabin surrounding the console in your boat the signal may be degraded outside of the cabin.
Actual signal reduction if any will vary from boat to boat. Should the signal be noticeably worse the range for wireless connection between the xFOB and the xHUB will be reduced and the system can go into MOB mode which will cause unintentional engine stops.
We recommend in this case to use an extended cable for the antenna which can be set up outside of the driver cabin/console.