YES.
NMEA2000 certification requires isolation. So if you are generating ground loop, you should use isolated tranceiver (e.g. ISO1050) and either isolated PSU or separate power feed on your device NMEA2000 side. If you do not do isolation you may have funny problems, which are difficult to find. The most critical are those, which start to disturb communication on the bus. Even you do not need certification it is better to think carefully in advance.
Wiki provides good article about ground loop, so there is no need to repeat anything about that subject.
When you desing your device you should check are you going to have ground loop in your system. If you simply measure e.g. temperature with separate isolated sensor, you can power your device from N2k bus. If you measure e.g. from pressure sensor and it is not isolated from ground, you should have isolation on your N2k side. If you measure digital states, you can use optoisolators on your digital inputs and power your device from N2k side.
On boat all your device will be normally powered from same ground, so there should not be common-mode voltage issues.