4788 Air Horns
I've repaired or replaced almost all of my air horn systems on my 4788 and questions about the air horns on both the 4788 and 4588 keep coming up on The Bayliner Owner's Club. Therefor, I'm going to summarize the information I know about older 4788s and it seems to be later 4588s.
The airhorns have a big scripted S on the back of them. They are the Signaltone Tornado model. The current manufacturer in the United States is Fiamm America. They are located in Michigan and you can reach them at 231-775-2900. They will tell you that you need their repair kit number 21340. They don't sell it directly, but they will refer you to:
Speed's Carquest of Cadillac
423 N Mitchell St
Cadillac, MI 49601
Ask for Ralph.
The compressors are made by Grover Products. Mine is hidden behind the ice maker below the stereo cabinet.