There is a thing called an "SWR meter" which checks SWR (standing wave ratio) as a measure of how well the aerial is working.
If you broke it off and didn't replace it immediately, a strong possibility is that you have got water in the coax cable, which will bugger it up immediately. Also worth doing a basic continuity test on the coax to make sure it is connected but apart from physical damage, 90% of problems are due to water ingress in the coax, and that's on vehicles, on boats it is probably even worse! Water ingress can be due to poor sealing at either end or physical damage to the coax outer e.g. if it runs across the deck and has been pinched or stomped on.
A Boat is a hole in the water, surrounded by fibreglass, into which you throw money...
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