Sound Proofing

[mattinri]

I've got an offer on my boat so the serious shopping has started. I'm looking at a 31' Willis Beal with a 315 Yanmar. Full cabin, wet exhaust. the cabin sole is raised probably 3". I really liked the boat but my wife complained about the engine noise at cruise. The owner had installed Sound down (the cheaper version - less thick he said) over the engine. I'm wondering how much quieter I can get it if I sink some money and effort into it. Anyone care to guess how much mooney and effort it might take? Right now you have to talk very loud, but not shout to be understood in the cabin - sorry, no decible reading device

 

[CEShawn]

Depending what your helm area is like, you can add that noise dampening under layment for a carpet. We did that and then used a indoor/outdoor carpet, nicer than the green turf of course and that made an improvement. That under layment came from Hamiltons. Then of course a head liner would always help... Lots you can do too... Usually takes a little while to tweak down... I think that underlayment was $400 but cabin size was larger, that indoor/outdoor used to make it a couple seasons too... Then go through and make sure all your engine hatch's are tight, not letting noise through, those are the ones that make a big difference. I used to go around while it was running to make sure when I opened a cabinet or door that the engine sound didn't pass through. Its amazing when an engine is running, if its not properly ventilated how it will "suck" air from all sorts of places making high pitched noises. Its an art almost!

 

[Nighthawk]

the 6LP Yanmar is a pretty quiet engine (I have two of them) so I suspect the current noise reduction efforts on the boat was half hearted. I wouldn't let the current noise turn you off to the sale if otherwise the boat is to your liking. Although it's messy and a PITA job ripping all the current noise reduction out and doing it right is a nice winter project and easily a DIY job. You want to attack this in three ways, first the entire underdeck of the engine compartment (consider using lead in the layering), an acoustic carpet underlay on the deck and then sealing 'openings'. Many times an engine compartment is well insullated but there is a huge opening around the gear and/or shaft leading aft and the noise then resonates aft to a deck with zero sound reduction.

As stated above this can be an art form. Sometimes sound reduction is simple, sometimes the construction of the boat makes it more difficult to seal all the sound paths. I am convinced that with a little effort you could significantly reduce the current noise levels and put a smile on the admiral's face.

 

[tunaorlater]

Every hard surface of the engine compartment should be insulated, except the bottom itself. Noise bounces around so the insulated surfaces help avoid that. Everything you do will slowly help reduce the noise.

 

[Eslang]

I had one of them in my 28'. It was the 260 version. Even though it is quiet, it turns 3800 rpm. Hard to quiet a screaming engine. Higher the rpm the more decibels its put

 

[BillD]

I've got an offer on my boat so the serious shopping has started. I'm looking at a 31' Willis Beal with a 315 Yanmar. Full cabin, wet exhaust. the cabin sole is raised probably 3". I really liked the boat but my wife complained about the engine noise at cruise. The owner had installed Sound down (the cheaper version - less thick he said) over the engine. I'm wondering how much quieter I can get it if I sink some money and effort into it. Anyone care to guess how much mooney and effort it might take? Right now you have to talk very loud, but not shout to be understood in the cabin - sorry, no decible reading device

Better to be "safe" than "apologizing" to the old lady (wife).

Buy the boat with the knowledge that "this is as quiet as it will get".

If you can make improvements....GREAT !!!! it will be a bonus.

When I repowerd the Blackfin with new Cummins 6BTA 370s (same as old motors) I added a lot of insulation over and above what the Blackfin factory did.

Didn't make much of a difference.
Two Cummins screaming @ 2600 with turbos etc., under your feet EVEN with all the plastic windows rolled up, GETS PRETTY LOUD !!!!

FWIW,

Bill D

 

[petrel]

2600!?! I'm curious; how many hours did you get out of the first pair?

 

[BillD]

2600!?! I'm curious; how many hours did you get out of the first pair?

Petrel,

Not sure how many hours were on the old 370s.
Got "snookered" on the sale by being an "under educated" marine diesel buyer, a lousy Cummins engine surveyor I hired and a FL boat broker etc.
Enough said.

The 370s in the Blackfin had "reportedly" 550 hours "validated" by the original VDO tachs. We we burned one of the 370s up the 1st year (2008)by a fluke belt tensioner snapping off....come to find out both 550 hour engines had already been rebuilt twice !!!! Lesson learned.

Back to your concerns about cruising the 370s @ 2600 rpms...ZERO issue "IF" you have the engines propped to 3150, (I do) have loss of raw water alarm switches, (I do) one or two high coolant temp switches/alarmed and monitor turbo boost and EGTs. (I do)

Actually cruising @ 2550 rpms is the "sweet spot" for the 31 Blackfin/Cummins 370 combo!

 

[petrel]

I'm used to a 315hp B series in a 31 BHM. 2600 is only 200 off the top and a lot more fuel than say 2300. 3150- Holy Shit.

 

[BillD]

I'm used to a 315hp B series in a 31 BHM. 2600 is only 200 off the top and a lot more fuel than say 2300. 3150- Holy Shit.

The 370 is rated @ 3000 WOT

2600 is 400 off the top, no big deal really "IF" the engine can ALWAYS reach rated using the boat as heavy as one would .

Prop the 370 to reach 3100-3150...gives ya a bit of "cushion" on the %load running in the upper cruise rpm ranges.

 

[jerseysportfisher]

Sound proofing.....

Using the cheap shit foam does not do anything other then take some high frequencies out. It roughly gives you about a 10 db drop. The best sound proofing materials are those with more mass to actually absorb the sound. Products like dynammat and hush matt are ok for containing panel vibration. Closed cell foam does good on certain frequencies. Mass loaded Vinyl, does really well on sound deadening, however being a plastic, i'm not to sure on how well it will do sitting on a turbo charger. So what options are there ? Well The old school way which is proven that works extremely well, leaded engine blankets.

 

[mattinri]

Interesting. The 31' Willis Beale with a 315 Yanmar was very loud. I was just on a 35' T Jason with a 225 John Deere with even less sound down and it was noticeably quieter. I guess the hull and below-deck configuration also plays a factor.

 

[petrel]

What does the Deere turn compared to the Yanmar? I'm guessing the Yanmar is a screaming banshee by comparison. My Cummins B series gets loud as hell at high RPM's.

 

[steveinak]

What does the Deere turn compared to the Yanmar? I'm guessing the Yanmar is a screaming banshee by comparison. My Cummins B series gets loud as hell at high RPM's.

my 6068 wot is 2650, i run it at 2000 to maybe 2200 for cruise. Its pretty loud but its all exposed downstairs and pretty much bare walls.