Unless you are restoring to "original", I would suggest getting a "real noise maker". Those small horns won't even wake up the crew or disturb the fishing. While I suggest a true air horn(s) w/ compressor, the "electric versions" would be a substantial improvement.
Remember, the whole point of even having a horn is to be heard by a bridge tender a mile away, in an air-conditioned hut, or by another vessel in motion ( with all those noises involved ).
It is a safety issue, and louder is better. IMHO.