41PC Sound reduction / Sound proofing


B

Brians3000gt

Member
Hey gang,

So, last season I noticed that the engines/vibrations are just too loud so I decided to measure. I'm getting 80-85 decibels over the hatch while cruising. I was wondering if anyone had tried upgrading the sound proofing material in the bilge and if so, how it worked out. I was reading through a few other people's write-ups on The Hull Truth and it seems like for our diesels that SoundDown 2" 2lbs is the way to go for under the floor/over the motors but I don't think that will be enough. Additionally, Walker makes newer "QT" edition Air Sep air filters/intake that retrofit to our Cummins 6CTA's and the VP of sales, Mike, who I've been talking to is claiming something in the realm of 5-8dBa reduction from these, however they are $1130 a piece!!! Any/all thoughts appreciated. Also, I would be open to the idea of a "group buy" on those air filters if they would give us a reduced price.

Best

Brian
 
I did a posting about adding 2” Soundown insulation on the engine hatch on our 41PC. It is in this section. Unfortunately I didn’t measure the sound levels before I did it because when we hauled for the winter I didn’t plan on doing it this past winter. We haven’t launched yet so I don’t know how well it will work. But after we launch I will give my impressions of the sound levels. The post is on the second page of this section.
 
Dave, there is a couple phone apps, one is NIOSH SLM and the other is Decibel Meter and they are both free. You should download them and test your levels when you splash. I am dying to know how you made out! Also, did you only do under the hatch itself or did you do some of the surrounding floor areas around that?
 
I can do the dB testing now but unfortunately I didn’t do it before I did the insulation so I don’t have a baseline to compare it to. So far we have only done the big cockpit hatch and where the refer used to be. I bought 2 sheets of the insulation and I have a fair amount left. I am going to add some around the outsides of the big hatch when I get time this summer. Since I have it I might as well use it.
 
I kept the original insulation for about 2” where the hatch seals against the drain trough. It seems pretty good and makes a fairly tight seal. What RPM do you get 85 dD?
 
That's cruising speed, roughly 1800-2000, I'll recheck and get an exact measurement this weekend when I zip around the bay and post pics here in this thread.
 
I have a dB app on my phone. We are going to launch next Friday, I hope. It is a short run from the haul out to our house. Don’t know if I will even get it on plane then but will try to get a measurement in the near future.
 
So I to have been wondering about the sound so i decided to load the app on my phone. I get about 85 to 87db while cruising. However everyone else's vessel ive been on has been the same in the rear cockpit. I will do the sound deadener but i am not overly confident it will help.
 
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