Stainless Steel
Thru-the-Transom
4 inch Exhaust Tips
Straight through
exhaust tips are
4
inches in diameter and
10 inches long with 5
inches inside the
flange and 5 inches
outside the flange.
The exhaust tips
come with external
flappers for easy
replacement (no
need to remove the
tip to change the
flappers).
Stainless Steel
Thru-the-Transom
4 inch Exhaust Mufflers
The muffler has a 4 inch outside
diameter with a 3 inch inside diameter.
The muffler core is perforated and
packed with stainless steel sound
deadener. The straight-thru design
silences without restricting exhaust
flow.  The tapered outlet reduces
the
"rushing air noise" as the fast moving
exhaust gases exit the muffler.
The inlet to the muffler is tapered to
funnel the exhaust gases into the
muffler from the 4 inch rubber exhaust
hose.
The mufflers are 10 inches long with
5 inches inside the flange and 5
inches outside of the flange.
Internal flappers add considerable
amounts of restriction to exhaust
flow.  External flappers have zero
exhaust flow restriction and do not
make noise like rubber covered
metal internal flappers.
       Exhaust flappers are the
most important component in the
exhaust system of a marine
engine.  Not only are they
required to keep water from
entering the exhaust when the
captain cuts the power ("following
seas")  but are extremely
important when the boat is sitting
in a slip or beached with the
engine shut-off.  Waves and
wakes can fill up an engine very
quickly.  
       The exhaust flappers should
be inspected and replaced
regularly.  External flappers can
be inspected at a glance and
changed with a screwdriver (while
the boat is in the water!).  The
exhaust tips need to be removed
from the transom to change
internal flappers.  
       External flappers are
sometimes called "Salisbury
Flappers" and are available at
most boat stores and marinas.
They are modestly priced and a
spare set can be easily stowed in
the boat.
       Internal flappers come in
many different styles and are
usually only available through the
manufacturer of the exhaust tip.
The Importance of
Exhaust Flappers