Hi there nic420, Just so you're aware, the bravo drive from mercruiser was first introduced in 1988. If you have your drive serial number normally found on the side of the upper drive shaft housing, one of us might be able to help you with the correct year if needed.
Is this boat/stern drive new to you? Did it just start grinding?
During shifting, you should be promptly going into gear. Going slow could create a grinding type sound.
Any chance of posting a video of the grinding noise?