Cockpit Noise Reduction

[Jimmy]

I am working on reducing the noise in the cockpit area while under motor. To accomplish this I need to do two things.....
1) Replace my "worn in " blower .....it is a little too loud for my liking , and I choose to run not only before starting , but at all times the A-4 is running , and on hotter days , for a few minuets afterwords
2) Add sound insulation. Currently have none , with the engine directly below the cockpit area. Access is thru the companion way stairs and starboard lazzeret. (I have a pretty good water muffler.)

What is the quietest blower motor out there?
What type of insulation would you suggest?

I actually like the sound of the engine , purring at my feet , however the wife has a different though.....so I need to reduce THIS noise , so others will automatically go away

Thanks

[Dave Neptune]

Jimmy, I too hate undo noise on the boat and I am a stickler for running the blower~before~during & after running the engine. My blower is mounted just ahead of the exit horn on the transom. I mounted it to a bulkhead with vibration isolators used in some automotive electric fuel pump mounts. I got them from Mazda I believe they were on the RX-3 & 4's where the pump mounted under the rear qtr panel. McMaster Carr probably has something similar. They have been in service for many many years now and you can barely hear the blower. Once the engine is running I occasionally check to be sure that it is running. My blower is a 4" and a plastic frame. I have no idea what brand it is, I bought it at a marine supply probably over 20 years ago. It is mounted high on the bulkhead in a dry spot ajacent to the lazerett. I have had many comment on how quiet my boat is when motoring , a good thing.

Dave Neptune

[msmith10]

As Dave mentions, unless you put some type of rubber isolators between the blower and whatever you mount it to on the boat, it will be noisy. The same thing with the engine. I lined my engine compartment with 1/2" foam/lead layered silencing material. It helped a little. However, with my engine hard mounted to the stringers, without any rubber insulators, it was like putting lipstick on a pig.

[sastanley]

Hi Jim, I love this stuff...it is really a heat shield, but likely helps with noise as well. My engine is in the middle of the boat, so I don't quite have the noise issues when all the 'holes' in the cabinetry are closed. I tend to keep them open though, because I want to hear any changes in the old girl's temperment.

heat shield at Amazon.com

I'd also recommend checking out magazines like Good Old Boat...they have advertisers that have some engine box insulation solutions also.

[hanleyclifford]

check this out - http://www.defender.com/product.jsp?...02333&id=96126

[jpian0923]

Some have reported success in quieting their engine by filling it with diesel oil. I have not tried it but others that have, might want to expand on the discussion.

[Dave Neptune]

Jim, I think waht you are refering to is using a heavier viscosity oil. Running "thicker" oil will quiet a bit of the mechanicle noises for a while but as it breaks down the noises will get louder. It really doesn't make a big differance. There is no substitute for good insulation.
I too have the engine in the middle of the boat and the box "around" it is the end on the dinette. I added some additional insulation along the sides only and cut to fit close to the hull further insulating the noise that radiates through the cabinetry along the hull. When I open a door or drawer ther is no longer a lot of noise eminating from them.

Dave Neptune

[hanleyclifford]

Originally Posted by jpian0923

Some have reported success in quieting their engine by filling it with diesel oil. I have not tried it but others that have, might want to expand on the discussion.

I agree with Dave that thicker oil will not do the whole job but it sure quieted my engine down a lot and I also have the insulation. It was Mo who put me onto the 15w40 diesel oil and it has done very well from Edgartown to this point (Langford Creek).

[jpian0923]

My apologies. Didn't mean to imply it was the whole solution...just part of it. Every little bit helps though.

Have you tried ear plugs for the wife?...or for you? (so you can't hear her complain)

[sastanley]

hmmm .....interesting discussion. I have lots of 15w40 Rotella floating around in the garage after my Cherokee SUV was crushed by Hurricane Irene, since that is what I ran in that to keep her from smoking too much. The P.O. of my boat was running Mobil1 10w30 in the motor and I am currently running Rotella SAE 30w in the motor.

I like to hear the motor running, but in reality I think we agree, the quieter the better, which means less friction...

I am not really providing any insight, just my personal experience.

[Jimmy]

Thanks for the responses.......
I never thought about rubber washers/spacers for the new blower , but it makes great sense. Do you think it matters where the blower is located?
I am thinking of mounting it low , in the engine compartment , so I have easy access ,and the noise it does generate wont verberate between the inner and outer layers of fiberglass up , inside the transom.

I was surprised to see a lead layered insulation blanket. I would have thought simple fiberglass insulation with a foil covering would be sufficient.

Think I will stick with the straight 30 weight oil I am currently using (Diesel). I did a little research here , and that seems to be the oil of choice . The engine, and all her innards sound right. Not messing with a good thing.

[tenders]

Put the wife on somebody else's diesel-powered boat for a few hours and she won't notice the A4 sound at all.

[Dave Neptune]

Jim, I used isolators not washers. An isolator has a stud out of each end of a piece of rubber or a mounting plate and a stud, kinda like a motor mount only smaller. My mounts have 5mm (about a 1/4") studs. The studs re mounted in the rubber and not connected with anything but the rubber. You can mount the blower to a sheet of rubber and then mount the rubber to a bulkhead and just let it hang there. The 'vibration and noice need to be "isolated" via the rubber to really make a big differance.

Dave Neptune

[sastanley]

Jim, you want the blower NOT mounted in the bilge. Remember the blower's job is to evacuate gasoline fumes from the bilge. They mount them away from the bilge so they can't start a fire when turned on (click! = spark) if fumes are present. They are up in fresh air usually near an aft bulkhead...Once running, there is no fire danger, so they can safely pull the fumes out.

[Dave Neptune]

Jim, take a look at these @ McMaster Carr. #9376K2 1/4" & #5823K5 stainless 1/4". These are both avbailable in rubber or neoprene, you can also find urethane however I would use the neo. personally.

Dave Neptune

[Jimmy]

Shawn
I made the mistake of presuming that all blowers are sealed, to prevent spark at start up. I can't fathom using a unit that isn't
doing so makes about as much sense as using a match to illuminate your filler tank at night.....so your certain to not over fill when refueling
Jim

[sastanley]

Jim, they may well be sealed.."ignition protected", but I guess mounting them away from the bilge is an additional safety factor.

I probably should have stated in my last post that it was my opinion that is why they do that. I don't build boats, so I could be wrong.

[jpian0923]

My blower is mounted in the stern locker, from about a foot to the transom exit, connected to a long hose that hangs about a foot off the the bilge bottom. Not my design. It was this way when I got the boat. Must be some science to it that I won't mess with.

[JOHN COOKSON]

If the blower intake is on the bottom of the bilge it will pick up the heavier than air gas fumes.

However:
When the bilge has some water in it the inlet tube will either (A) be under water or (B) float on top of the water.

TRUE GRIT

[David Masury]

I see that you own a c&c... I own a c&c 27mklll, the noise your are hearing it simply the tract that these boats were made somewhat thin. You can add insulation above the engine and as far as the blower goes, get another that maybe more quiet... The A4 is not that noisy compared to a diesel.

I would be satisfied if the engine ran well and got me to where I needed to go..
Actually mines runs quite well, thank you.

David

[Bold Rascal]

My A4 runs fairly quiet as well AND, I like being able to hear it while it's running, at least for the time being.