[giff1]

My air horns are not sounding but the compressor is making a growling sound.
I can hear the compressor under the helm.
Where is the compressor located. I'm planning to check the air coming from the compressor then check the air at the horn. I have a 2000 3500 express. Any help would be appreciated.

[ReelMagic]

Common problem w/air horns... I own a 38' Open and have fixed similar/same issue several times in the 15 years I own the boat... Salt gets into the horns somehow. Most likely salt air is the culprit... Believe the fix is as follows, at least it resolved my problem multiple times.... Remove the air horn covers (3
screws on top of the air horns themselves). You will most likely see a plastic diaphragm that needs cleaning. Also, you need to ensure the center pipe top lip where the compressor air comes out to vibrate the diaphragm is smooth/clean.... The top of that pipe is most likely rough/covered with salt.. Use Emory Cloth (very fine sand paper) to smooth the top so the diaphragm can seal to the top of the pipe.. Do both air horns and I think this will correct the problem... M2C

[The Duke]

My 06, 38 open had same problem.   I found a rebuild kit for around $9.00 from Grainger.  if you’re going to take the caps off to clean it out, you might as well change them.  Really easy to fix.  If you go this route, remember the caps are plastic so don’t use a screw gun when replacing. Just snug them up by hand. I also ran a piece of stiff electrical wire down the air line from the roof while I had someone holding the horn button down. This will help make sure the tube is unobstructed and if there was some debri that got in there, the air flow will purge it.  I was unable to include the link but here’s what you should check ou from Grainger. 

FIAMM Horn Replacement Kit: Air, 3 in Lg, 3 in Wd, 1/2 in Ht, 3 in Dia.
Item 53CU34
Mfr. Model 21323