Engine soundproofing

[RichardS]

The ideal is perhaps to have an extractor fan taking hot air from the top of the engine compartment, plus a ducted supply of cooler outside air (which can usually be arranged so that it allows the cool incoming air to blow on the alternator).

As for fan noise, my boat has a factory-fitted extractor fan which intriguingly is a 24v fan running on a 12v supply. It's quiet!

Indeed. I wasn't very clear but my engine blowers are blowing outwards so perhaps "suckers" would be a more appropriate term.

Richard

 

[GTom]

These people don't share your view:

Vehicle acoustic engine blankets - NK Group

I don't have any experience of their blankets, but I used their lead/foam/foil sheet to line my engine bay in the traditional way and it was very effective.

Pete

I'd not use that on a boat engine. I case your engine is overheating for whatever reason, the blanket will just make things worse, reduce your time available to react.

I am out on the market for a new engine-room lining, anyone tried reasonably priced car sound proofing mats like this one? https://www.amazon.co.uk/Noico-deadening-Automotive-Insulation-dampening/dp/B01KZ5X7KO

 

[coopec]

I'd not use that on a boat engine. I case your engine is overheating for whatever reason, the blanket will just make things worse, reduce your time available to react.

I am out on the market for a new engine-room lining, anyone tried reasonably priced car sound proofing mats like this one? https://www.amazon.co.uk/Noico-deadening-Automotive-Insulation-dampening/dp/B01KZ5X7KO

Looks quite expensive?

 

[pvb]

I am out on the market for a new engine-room lining, anyone tried reasonably priced car sound proofing mats like this one? Noico 80 mil (2 mm) 10 sqft (0.95 sqm) car Sound deadening mat, Butyl Automotive Sound Deadener, Audio Noise Insulation and dampening: Amazon.co.uk: Car & Motorbike

That sort of thin self-adhesive sheet is used in cars to help stop panel resonance, rather than to deaden sound. You'll also often see it on the underside of thin stainless steel sinks.

There's so much work involved in fitting sound insulation that you might as well use decent stuff and be happy with the result. Halyard make some good stuff, called Siderise. If you used that in 32mm thickness, I reckon you'd be very pleased. It's also fire resistant and fuel/oil resistant. It is considerably more expensive (about 4x the price of the Amazon stuff), but it works!

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[rogerthebodger]

I used similar to what pvb posted in my engine room.

Mine is held in place with sheets of weld mesh 2 mm rod mesh about 25mm x 50mm. No droop in over 10 years of use.

Also make sure that any joints will not allow direct noise flow at the joints in access panels.

 

[peter gibbs]

Is there any reason why an engine should not be covered with an insulating blanket rather than sound-proofing the whole space?

I accept that the engine becomes hot during operation but is not the water cooling within the engine sufficient to keep it sufficiently cool?

Just wondering.

Total engine soundproofing is not feasible on pleasure yachts for reasons others give here, not least between engine and bilge but every little helps.
Many boat builders use the foam egg box open texture type of proofing which we soon all learn is nominal at best. You need the type with a sound deadening layer sandwiched by foam. Not cheap!
Lay on slabs to sides and top of engine compartment, screwed and glued, for worthwhile benefit. Remember trapped air is proofing - so avoiding this layer by gluing direct to the engine is counter-productive.
PWG

 

[lynallbel]

I went mad and covered pretty much the whole of the engine bay with extra sound insulation, all lockers in the cabin lined with sefl adhesivee neoprene foam, all hatch seals repalced with neoprene.
It has made a big difference.

Panel resonance has been mentioned above, and that is what I was aiming for in the bay itself, ie not total coverage just all large flat surfaces, but in the salloon (if you can call it that!) I was after total air tightness.

Even lining the large lazarette lid made a difference.

 

[GTom]

That sort of thin self-adhesive sheet is used in cars to help stop panel resonance, rather than to deaden sound. You'll also often see it on the underside of thin stainless steel sinks.

There's so much work involved in fitting sound insulation that you might as well use decent stuff and be happy with the result. Halyard make some good stuff, called Siderise. If you used that in 32mm thickness, I reckon you'd be very pleased. It's also fire resistant and fuel/oil resistant. It is considerably more expensive (about 4x the price of the Amazon stuff), but it works!

I'd do that when I replace the plywood panels the engine room is made of then. At least 3-4 panels are due for replacing. We don't use the engine too much, however, there is a lot of vibration and noise when it's running.

 

[pvb]

We don't use the engine too much, however, there is a lot of vibration and noise when it's running.

Maybe worth checking the condition of the engine mounts, and the alignment of the propshaft coupling.

 

[GTom]

Maybe worth checking the condition of the engine mounts, and the alignment of the propshaft coupling.

Will do. Old rusty mounts, probably a good idea to give them some proper care.