Has engine soundproofing improved in the last 30 years?

[fredrussell]

My trusty old Yanmar 3GM has its bay lined with the usual ‘foiled foam’ soundproofing. It’s not the quietest, being a 30 year old diesel, and I’m wondering what soundproofing modern engines have? Have things moved on? Has anyone changed from foiled foam to something newer and noticed a big difference?

 

[RupertW]

My trusty old Yanmar 3GM has its bay lined with the usual ‘foiled foam’ soundproofing. It’s not the quietest, being a 30 year old diesel, and I’m wondering what soundproofing modern engines have? Have things moved on? Has anyone changed from foiled foam to something newer and noticed a big difference?

The biggest difference we found was changing the engine mounts when the boat was 11 years old.

 

[john_morris_uk]

Agree with comment regarding engine mounts with the addition of the biggest difference for us was fitting a Halyard Marine Aquadrive. It completely isolated the engine from the hull and with lots of soundproofing around the engine bay, you can barely hear our engine from the cockpit.

 

[prv]

The new soundproofing I put in a few years ago still used foil and foam, but also a layer of lead sheet suspended in the middle of the foam. That's not new technology, just more expensive than many boatbuilders want to use. A combination of the better material, and more thorough fitting (sealing all gaps rather than just sticking a couple of panels on the main bulkheads and calling it job done) made a very big reduction in noise. Before, someone in the cabin wouldn't know that someone in the cockpit was calling for them unless they really shouted. Now you can hold a conversation easily between the two.

Pete

 

[fredrussell]

Hmm, I suspect my engine mounts are also 30 years old. £600 a set, I believe, for proper Yanmar ones though. Ouch.

 

[Rappey]

Im sure the foam itself is vastly improved in type and efficiency, and the heavy lead barrier on the higher end insulation now replaced by some sort of plastic whilst all of it being heat resistent and flame retardent.

 

[Moodysailor]

Used loads over the years, the best i've ever found was the Halyard sheets with the barrier sheet. To get the best noise reduction though i've often found it's not the quality of the sheets, but the application that is more important - the time time spent covering all gaps and getting into all the small areas is a better investment than that best quality sheets.
In general though - go for the thickest sheets you can install, cover all the gaps, and get sheets with the barrier layer.

As others have mentioned above, noise often comes from other areas though. In a conventional shaft drive boat, the engine mounts do dual purpose of providing forward thrust and isolating the engine from movement. So ensuring these are in good condition and isolating as much from the shaft as possible is also good (someone mentioned an aquadrive above - these are brilliant).

Also, you can do a lot to reduce vibration by checking your exhaust run. If flexible exhaust hose is hard against any bulkheads, stringers, etc then this can also transmit a fair amount of vibration.

With thought, a fair amount of time and a little money, a lot can be achieved.

 

[dankilb]

I’m hoping to source some of this -
Quietpad | Marine Soundproofing | Quietstone Acoustics

...it’s certainly evolutionary (foil faced foam with a deadening layer) rather than revolutionary. But I’m interested to see whether a) I can source some from the manufacturer at a reasonable price (they’re local to us) and b) whether it’s any better performing than the regular chandlery variety.

Our engine compartment is stripped back to the bare plywood so needs something and given the high cost for lead-layered foam from ASAP etc., I’m inclined to experiment!

 

[Moodysailor]

I’m hoping to source some of this -
Quietpad | Marine Soundproofing | Quietstone Acoustics

...it’s certainly evolutionary (foil faced foam with a deadening layer) rather than revolutionary. But I’m interested to see whether a) I can source some from the manufacturer at a reasonable price (they’re local to us) and b) whether it’s any better performing than the regular chandlery variety.

Our engine compartment is stripped back to the bare plywood so needs something and given the high cost for lead-layered foam from ASAP etc., I’m inclined to experiment!

It's definitely the construction I would recommend. It will be interesting to hear what thicknesses they can offer.

Good luck.

 

[geem]

A lot of people dont realise how important it is the fill the tiniest gaps between the sound insulation. If you imagine you are building a swimming pool you won't go far wrong.

 

[rogerthebodger]

I’m hoping to source some of this -
Quietpad | Marine Soundproofing | Quietstone Acoustics

...it’s certainly evolutionary (foil faced foam with a deadening layer) rather than revolutionary. But I’m interested to see whether a) I can source some from the manufacturer at a reasonable price (they’re local to us) and b) whether it’s any better performing than the regular chandlery variety.

Our engine compartment is stripped back to the bare plywood so needs something and given the high cost for lead-layered foam from ASAP etc., I’m inclined to experiment!

That very similar to the stuff I used. but as geem says ensure you have no gaps. Also ensure the is no way sound can escape around the edges of removable hatches

Foam draft excluder is a good way to stop any sound escaping.

I also used a thin weld mesh to prevent the sound insulation from coming unstuck and drooping

 

[dankilb]

Gaps are certainly a particular challenge for us (and similar AWB aft cockpit designs...). We've got 5 (yes!) separate openings into the engine compartment to afford access - the companionway steps, a small door port/aft, and two separate removable panels aft. All in plywood so gaps a plenty and not particularly sturdy.

So I'm already pondering a mix of rubber seals and foam draught excluders...

As satisfying as it was got have the whole compartment stripped out, de-stickied from the old adhesive (no mean feet!), sanded and prepped - it's quite a bit of work to reinstate it all and end up with something soundproof, fire safe, with enough clearance, and looking decent. And I reckon I'll struggle to get change from £2-300 once it's all done.

As none of the panels alone are have a large area - and the horizontal/overhead ones will be the smallest - I'm hoping to get away with plastic washer-type things with screws as a backup in case the self-adhesive fails. I'll also prime the ply with the epoxy primer I use everywhere to give a stable substrate to aid the adhesive.

 

[earlybird]

For airborne noise insulation, foam is most effective at the higher end of the sound frequency spectrum. A dense barrier layer such as lead is required for the lower frequency end. Also, as said, decoupling the mechanical bits with good engine mountings and, especially, an Aquadrive, is very effective.

 

[matt1]

I had a Halyard aquadrive on my last boat (Yanmar 3YM 20) and their 45mm double barrier insulation. It was VERY quiet ;-) I only realised how quite when I bought a new boat. The insulation was very heavy though

 

[fredrussell]

Thanks for all the replies, plenty to consider there. A few people have mentioned getting rid of air gaps in soundproofing - my engine access panel (usual thing, lower half of companionway steps) has an air vent fitted through which, I assume, combustion air is drawn. For you guys that have eliminated all gaps, where/how does combustion air enter engine bay?

 

[rogerthebodger]

You can still have the air vent but make sure the is no direct line for any sound to escape also put sound insulation around the vent baffles.

The air for my engine comes via the bulge and a sealable outside vent pipe.

 

[WoodyP]

I have thought about doing something similar but am concerned that the reduced air space around the engine could contribute to overheating. From the rear of the engine and gearbox there is a large area holding the water tanks.that would have to be blocked off. If I only sound deadened the grp moulding and steps that form the engine cover down that protrude into the saloon, would I be wasting my time?

 

[prv]

For you guys that have eliminated all gaps, where/how does combustion air enter engine bay?

In my case, through a vent in the side of the binnacle, up a short length of duct (to stop water coming in), over the top and down the inside of the binnacle. There are two three-inch pipes through the cockpit sole for the morse cables, steering chain, and various wiring, and the air comes in around them.

Enough engine noise comes out through the vent for you to know it’s running, but not enough to be annoying.

Pete

 

[pvb]

For you guys that have eliminated all gaps, where/how does combustion air enter engine bay?

My previous boat, a Hallberg-Rassy 352, had the air intake taken from a void in the cockpit area, via ducting which directed the incoming cool air towards the alternator. This seemed very sensible, but there was engine noise noticeable in the cockpit. I fitted a couple of baffles in the void, and glued foam-backed carpet on to them. This dramatically reduced the perceived engine noise in the cockpit.

 

[Moodysailor]

For you guys that have eliminated all gaps, where/how does combustion air enter engine bay?

A 'periscope' type baffle arrangement lined with sound insulation is the simplest. Soundwaves prefer to go in a straight line, so if you can incorporate a change of direction along with some absorption material this will greatly reduce airborne noise.

The caveat though - if this intake is also designed as a fire extinguisher port then this safety feature needs to be retained.