Do they work?

Work great at transferring your money into the sellers pocket.thats about it.

The snake oil of gas boats.
They originally came out for nitro engines in RC cars when they're on-and-off the throttle a lot. They were also short-lived with them also.
A waste of money.

Performance gain is questionable on many factors and variables and if it really made a difference just about everyone would have one in their boat....tend to be more for the on road type of 2 stroke engine vehicles. The thought theory is there, although how can it add fuel and air that has very little pressure to a closed / sealed container when the line and container must have a lower pressure before anything can enter?
I have never tried one myself ..I'm with Bob on this one.

Been there - blew 50 bucks - nice decorations -- waste of coin

You can see 'em at 45 sec of this video on the Canadian Boat

They reduce the pumping efficiency of the case by adding a lot of "remote" volume. And being "remote" as they are, any fuel/oil/air will separate ( fall out of atomization ) and become useless for power production or lubrication. Just more "stuff" to clutter up the hull, and yet another source for air leaks.

Funny how many new guys to boats, ask about these things year after year.

I used one on my HPI savage big block nitro truck. Didn't do crap either!! Seems a good expansion pipe works best. Just Wondering if I missed something out there. Thanks for the comments!! Rob

I sold a set on Ebay, I found them at a garage sale for $5.

made $25 minus $4. for shipping

On our small piston port engines they are going to decrease performance if anything.

The technology does work when properly designed on the reed induction engines they are made to work with.

Yamaha perfected the use of boost bottles on the two stroke reed engines they make and it was factory equipment on them for many years.

Yamy put them on reeds, and thats where they are best known.but they can and will work with any type of induction. I first learned about them in the early 70s from the popular motorcycle mag where they showed an installation on a piston port bike.
The bottle itself falls into the Helmholtz resonator category and can be tuned to whatever rpm you want, although the boost effect is over a limited range.
But as Fastrat and I researched a tuned airbox is a better choice if you aren't running a pipe. Its impossible to get a single cylinder engine to run a tuned airbox with a pipe but a multi cylinder engine its a peice of cake.
Fastrats built an airbox to the dimensions we came up with and was so effective on a can muffler sikk 27 that tuned airboxes are now illegal in stock classes that don't allow pipes.