Need a BANG! and Smoke (from 2-3/4 12ga shell )

This is not an off topic remark about activities between consenting
adults.

After a short read, this may be just the group of people that can help 
me out here.

Does anybody out there have a recipe for a 12ga that will make a big
bang and a lot of smoke?

For a special event in the upcoming season, I would like to use my
shotgun to start a very high profile sailboat race.

The 10ga. cannon we might normally use will not be available.  We load
that with a black powder because the racers are often far enough away
that the re****t will give them bad timing so they watch for the smoke.

When we have done this with a normal field trial load, there have been
complains that there is not enough smoke for those in all direction to
see it clearly.  Louder is better, it can not be too loud.

I don't want black powder near my old double.  I just found out that 
Pyrodex still has lots of sulfur and is only a little cleaner than black 
powders.  So those are out.

It there a something that burns faster (and is not corrosive) than the
normal shotshell powders?

Thanks in advance for any ideas.

Matt Colie