That is done with cutouts. Merc and corsa both make them among others.
They are about a grand. I have a set of corsas. Even when in the thru prop
mode you still get some noise out the thru hulls. I added slip-ins and that
made it bearable. Still not nearly as quiet as thru prop alone. If you are
after quiet regular thru prop is the best. Those bolt on mufflers are so so
if you have space. Smaller boats often don't have enough space under the
swim platform for them. They are usually pretty long. Another option is
inside lift mufflers but they have space issues as well. You'll find most
of these options to be quite pricy. You can get a used thru hull Y pipe and
the hook up usually pretty cheaply. You just need to pull the outdrive and
lift the motor.

"*JimH*" wrote in message
...

"JamesgangNC" wrote in message
k.net...
It almost always is an option. In most cases the engine has to be lifted
to get the pipe that routes down to the lower unit installed. There are
filler plates to cover where the thru hull tips are removed. Except for
lifting the engine it is simple work. You might look at slip in mufflers
but they will still be a lot louder than thru prop.

"*JimH*" wrote in message
...
We are looking at a nice 21 footer to use for water skiing, tubing and
general use on Lake Erie. The problem is that it has thru hull exhaust.

Is it easy to convert to an below the water exhaust (through the prop on
the I/O)? How much money in materials would be involved? Is it a do
it yourself project?






I have seen boats that can transfer from thru hull to thru the prop with a
switch. Any idea the cost of such conversion?