Horns

Do you guys keep a air horn on your yak to warn off power boaters? 

I bought one but only plan to use it for emergency.

I think you should save it for Sunday AM after the GS9 potluck.  Start walking around the campground and blasting it into tents as you go!  Make sure your health insurance is paid up, though.

I found some small ones at a dollar store, I tried to keep them in my pfd pocket, but the horn would detach from the canister, and the canister, no matter what I did would start to rust.  OS after a while I gave up on it.

I bought one but only plan to use it for emergency.

Mine's in a wtrprof box in the hull, easy to reach but not in a real hurry so......

I don't carry one, I do have a fox whistle though.
I can see a horn being practical in some instances, but I just haven't had enough close calls. The times I have almost been run over by PBs it has been nice and clear, and they for sure saw me.