Making the 21 footer quiet

[K7MXE]

Heres what I did to calm down the motor noise underway.
Really simple and always trying to improve but I did this.

Found a good stock of foam board like what is used in insulation on
RV's. My pieces for the most part were a inch thick and two foot square
and blue in color. I put them where ever I could in the space between me
and the motor. Front of the motor box got two and they go up and down
as you access the motor. Under the motor was tricky and I built a dam
of small pieces and entered through the sea water port. I put foam in the
cabinet areas both flat and vertical. I put it on the cabin sole and want to
do that better and think I would like to try some of that interlocking stuff.
Added weight to the boat is nil and the boat is more quiet. A transfer of
motor noise travels up the keel so anything you can do there helps as well.
Boat is quiet now and cost was next to zero so for me it was a win, win.
What have others done?

Bob Heselberg in Eatonville Wa

 

[john]

I glued some sonnex acoustic foam to the sides and top of the motor box and it helped with some of the noise. I like your idea of trying to get something under the motor and in the cabnites.
If I could get the noise down a little more that would be great , thanks for the ideas.
I think you are right about the sound traveling up the keel and into the pilot house area, Running mine at a few spots on the tach with door closed is tolerabe but, it would be nice to get the sound down just a little more.
Let you know if I come up with anything good over the winter since you gave us some good ideas for more spots to sound proof.

 

[gunterprof]

Bob,

Your idea sounds great. Two questions for you. First did you remove the existing insulation that came with the boat?
Second, how did you attach the foam? I see a winter project in the works.

Thank you,

Dan

 

[K7MXE]

Only insulation I know of was in the motor box. Only place I had any room there was in the forward part of the box.
I had enough room between the raw water pump and the box for two thickness and they are just wedged in there.
For most part everything is just cut to size a bit over and wedged into place as when I did the project is was more
of a experiment that I was happy with.
I would like to do the cabin sole better as have a rug over the foam that moves around and would like to try some
of the interlocking stuff mentioned on the C Brat site. Right now the big project is hooking up a class B AIS.

Bob Heselberg