Sound Proofing Blanket

[Teetime]

I am considering fitting a sound reducing blanket over the engine of my 40hp Yanmar. I would be most interested to hear anyone with experience of one of these. I am worried about the engine and more particularly the alternator becoming overheated.

 

[Talbot]

There was an article in PBO a few years ago concerning fitting heat and sound proofing around the engine bay / cant remember the name of the material off hand, but it is man made flexible stuff. Sound proofing demands that you eradicate any means of open passage of sound. This means that you have to provide another route for the combustion and cooling air to circulate.

 

[Gordonmc]

My previous boat was a wooden open-bilged Hillyard and conventional sound-proofing was not an option so I bought an acoustic blanket similar to those available from
http://www.noisekiller.co.uk/acoustic_blankets_products.asp
I don't believe the idea is to wrap the whole engine - I certainly didn't - but the noise reduction from the top end, especially tappet rattle, was significant (Thorneycroft T90).
The blanket was big enough to cover the rocker box with an overlap of two or three inches on three sides. The lead layer allowed the blanket to be sculpted around the profile of the head. I stopped short of the alternator. The blanket was not harmed by proximity to the exhaust but I lagged the water injection bend anyway.

 

[prv]

I bought an acoustic blanket similar to those available from
http://www.noisekiller.co.uk/acoustic_blankets_products.asp
I don't believe the idea is to wrap the whole engine - I certainly didn't - but the noise reduction from the top end, especially tappet rattle, was significant

That's very interesting. My 2GM20 is a bit loud, but the engine compartment is too cramped and inaccessible to add any more insulation. I can imagine a lead sandwich blanket round selected parts of the engine could do a lot to quieten it down.

Can you give us a rough idea on price?

Pete

 

[PTB]

Acoustic blankets

It is difficult to get an effective soundproof installation on older boats where the engine isnt really in a dedicated 'compartment'. My engine compartment is full of 'holes' into cockpit lockers, bilge etc. So. I wonderered why marine engine manufacturers dont have available the sort of acoustic hoods that you see over the valve /injector gear on nearly every modern diesel car? The noisekiller blankets are an option which work quite well I think, but are bit basic. I asked Thornycroft a few years ago if there was any reason why a hood couldnt be used .. they said .. 'make one yourself but let the alternator have a bit of air'. So I made a removable hood myself which has layers of acoustic foam/lead sheet profiled for the engine shape on a ply template all lined with thin gauge ss. It is held on with 2 wing nuts and is easily removed for maintenance.
I wouldnt say the sound reduction is up to a properly lined compartment but it is a lot quieter than it was .. partic diesel knock. I have had no overheating issues since fitting about 250 engine hrs ago. Phil

 

[Gordonmc]

Can you give us a rough idea on price?

Pete

It didn't strike me as being particularly cheap - around £80 if memory serves. That said, a lot cheaper than Halyard acoustic sheeting or thinsulate, neither of which would have served. I got the large size for a four-cylinder engine.
I did think of going a step further an getting a tailored blanket for the bell housing, but as most of the noise on a diesel is top-end and exhaust, it didn't seem worth it.

 

[rotrax]

My previous boat was a wooden open-bilged Hillyard and conventional sound-proofing was not an option so I bought an acoustic blanket similar to those available from
http://www.noisekiller.co.uk/acoustic_blankets_products.asp
I don't believe the idea is to wrap the whole engine - I certainly didn't - but the noise reduction from the top end, especially tappet rattle, was significant (Thorneycroft T90).
The blanket was big enough to cover the rocker box with an overlap of two or three inches on three sides. The lead layer allowed the blanket to be sculpted around the profile of the head. I stopped short of the alternator. The blanket was not harmed by proximity to the exhaust but I lagged the water injection bend anyway.

Hi, many years ago a freind was Gamekeeper for Lord March at Goodwood. He had an old Landrover-FUV something which was used to patrol the estate and carry out his duties. He asked me to cobble up some soundproofing for the engine to enable a closer approach to wildlife. I used several layers of old horse blankets from the equestrian managment school covered with canvas,the whole lot sewn together by the tack man and then held around the motor with the finest quality galvanised iron fencing wire.It was a remarkable success and enabled him to do his rounds and at the same time learn the places where he could expect to find certain species collecting in a far shorter time than on shank's pony. The engine became almost inaudible on tickover at ten feet and no overheating or potential fire risk was found. Today, reflective metalic foils are avalable which would have been a sensible addition had we had access to them. The soundproofing was,of course,kept away from the hot exhaust manifold!

 

[pcatterall]

I got one of the lead cored blankets for my Tranny camper. It does reduce the engine noise a bit and means that I can now hear the tyre noise!!
I guess though that I am getting good air flow even under the blanket so on a boat i guess there may be more heat around alternator etc. ( but less tyre noise!)

 

[Elessar]

It didn't strike me as being particularly cheap - around £80 if memory serves. That said, a lot cheaper than Halyard acoustic sheeting or thinsulate, neither of which would have served. I got the large size for a four-cylinder engine.
I did think of going a step further an getting a tailored blanket for the bell housing, but as most of the noise on a diesel is top-end and exhaust, it didn't seem worth it.

the acoustic blankets work out at about £160 including vat per square metre of material used to make it.

so a square generator with little waste is I suppose better than intricate shapes.

each one is custom made so you can do just the top or top and one side if you want to keep cost and weight down.

They have 5kg of lead per square metre in them.