In article rLzGc.17379$JR4.9020@attbi_s54,
"Tony Thomas" wrote:

Loosen all the linkage screws on the side of the carbs. With the throttle
at idle position, all the throttle plates should be down against the body.
Tighten all the linkage screws.
Now open the throttle to wide open and verify all throttle plates are
setting flat.
If one is out slightly - loosen and adjust to flat as the others.
Now back to neutral and verify all plates are the same.

Very simple on these engines.

Thanks! I noticed the bottom carb was not closing all the way, and I did
exactly what you suggested (it was a guess).

Somewhere I read that you could listen to the carbs through a hose. I'm
not sure why. But I tried it anyway. What I heard was the bottom one
making a more pronounced fluttering sound than the top two. What could
this be? A valve or something? Or the carb?

Would you mind helping me with another question?

I was taking the carb intake box off, while my wife was standing there
chattering at me, and therefore I stuck my screwdriver in and started
backing out the carb adjustment screws! I, apparently, thought I was
removing the airbox screws. I'm guessing these were either idle or
something else - screws. So I screwed them in gently and backed them out
2 turns, each carb. It starts and idles, but backfires and dies suddenly
if I run it up. I dunno, I goofed, and 3 carbs is a new thang fer me. I
can handle it, I just need guidance. I ordered a motor service manual
from iBoat yeaterday, but it won't arrive until the end of the week.