Quietening a boat

[Simpo Two]

I have a 27' GRP cruiser with a Yanmar 3-cylinder 40hp diesel inboard. And frankly it starts to get rather wearing after a while. Noise comes from two places, the cockpit floor and the exhaust.

The cockpit floor has two hatches which account for about 70% of the flat space. They are GRP with wood reinforcement, approx 1" thick in the middle but thinner round the edges. They shut out a lot of the noise but not enough IMHO.

The exhaust is 75mm rubber hose with a Vetus gooseneck, and originally exited under the small bathing platform. In an effort to quieten the exhaust I extended the pipe to the edge of the platform and fitted a Vetus muffler www.vetus-shop.com/vetus-muffler-mp75-75mm-p-527.h... in the engine compartment. Extending the hose stopped the platform resonating but the muffler seems to have no effect at all.

I really would like to get the boat quieter, and welcome ideas

[TTwiggy]

Sails

[Fittster]

TTwiggy said:

Sails

That's an expensive option, oars are much cheaper.

[Simpo Two]

I tried an oar, after the raw water inlet became clogged with weed courtesy of the EA. It wasn't a very satisfactory means of propulsion. Now, how to quieten a Yanmar...

[s2kjock]

Have you room for sound-proofing foam panels under the cockpit floor? I am sure my dad has fitted these in the past to older boats we had and IIRC they were fairly effective, assuming there is still sufficient air around about the engine to reduce any overheating or fire risk.

I think we have the same engine on our current 30' yacht and the OEM soundproofing stuff does seem pretty effective. Even things like keeping the aft cabin cushions in makes quite a difference in terms of absorbing sound that flows back from the engine.

Not sure about the exahust noise really - never a massive problem in boats I have sailed, although maybe just renewing aged/old fittings might make a difference in addition to the muffler?

[Simpo Two]

s2kjock said:

Have you room for sound-proofing foam panels under the cockpit floor?

I've looked at the various products available and in the end got so confused I gave up - too many options. Heat and fire aren't major problems I think as diesel isn't volatile and ventilation is out of the sides, not the floor. I understand that the type of noise to be stopped is important - this is a diesel operating at 1,000-2,400rpm.

s2kjock said:

Not sure about the exahust noise really - never a massive problem in boats I have sailed, although maybe just renewing aged/old fittings might make a difference in addition to the muffler?

It's a 2-year-old 3JH5E, so everything is effectively new. Other boats are quieter so it must be possible...!

[Huntsman]

At least you know its still running.

[AlexIT]

Do you have enough space to fit a waterlock?

We did on our boat and it made a massive difference, given that the original installation was basically a free flowing exhaust from the engine straight above water level.

I can't say what size would suit best but here you've got some choices:
http://www.vetus-shop.com/vetus-lp-waterlocks-c-21...

We also used some soundproofing material below the cockpit floor, but I can't recall what it was.
it is very similar to this, but with an aluminium finish on both sides, as it sits pretty close on the turbos.

[Simpo Two]

AlexIT said:

Do you have enough space to fit a waterlock?

We did on our boat and it made a massive difference, given that the original installation was basically a free flowing exhaust from the engine straight above water level.

Hmm, well I have the muffler and also a gooseneck (though I understand that's to stop water siphoning back into the boat rather than quietening). There isn't room for a waterlock as well - the so-called 'muffler' alone is about 2' long and despite having been recommended by Vitesse Marine seems to have been an entire waste of £160.

But it seems to me that all these boxes do is churn the exhaust/water mixture up a bit. Whatever happens in the middle, there is still exhaust and water exiting by a 75" tube at the back and that's what's making the noise...

Perhaps I should fit a waterlock instead of the muffler? It seems to do the job of a gooseneck as well...

[AlexIT]

I cannot say how better a waterlock is compared to a muffler, as I did not try this solution, but the sure advantage of the waterlock is that the exhaust gasses have to physically go through the water, thus reducing the sound-wave. It has also the advantage that it reduces exhaust gas temperature and smoke, which for us was also a big concern (early 1980's 5L Turbo Diesel engines).

[mickrick]

Have a look at this companies products http://www.halyard.eu.com/pleasurecraft/index.php?...
I did a friends Swan sailing boat engine compartment, with their sound deadening material quite a few years ago now, the results where really impressive. IIRC we used an foam that had an similar material to lead sheet in it, except it wasn't lead. It also had a silver cloth like covering which was heat and fire retardant.
The exhaust products are excellent too.
I will be using it on Svip when the time comes, along with a GKN Aquadrive to reduce vibration, and soft mounts to reduce noise through the hull.
http://www.gknservice.com/global/marine/aquadrive....

[Simpo Two]

Thanks Alex.

I suspect one big grey box is much the same as another - gas and water go in, gas and water come out. Can't see how anything gets any quieter... just increases back pressure.

ETA: Thanks Mick, I'll drop them a line.

[Fishtigua]

As Mick said, have a look a Halyard. Not only do they do the soundproofing but they also do a splitter. The exhaust gas leaves from one outlet but the water leaves separetley and silently from another.

I've fitted them to gen-sets, so they must work on small mains too.

http://www.halyard.eu.com/pleasurecraft/productdet...

[hidetheelephants]

mickrick said:

Have a look at this companies products http://www.halyard.eu.com/pleasurecraft/index.php?...
I did a friends Swan sailing boat engine compartment, with their sound deadening material quite a few years ago now, the results where really impressive. IIRC we used an foam that had an similar material to lead sheet in it, except it wasn't lead. It also had a silver cloth like covering which was heat and fire retardant.
The exhaust products are excellent too.
I will be using it on Svip when the time comes, along with a GKN Aquadrive to reduce vibration, and soft mounts to reduce noise through the hull.
http://www.gknservice.com/global/marine/aquadrive....

+eleventy twelve. What Halyard don't know about making boats quieter isn't worth knowing; they aren't cheap but their stuff works.

[XJSJohn]

Remember, when fitting the sound insulation its not just teh underside of the cockpit sole that you need to be insulating, but the sides of the hull and bulkhead within the engine compartment, and sides of fuel tanks etc -

for the exhaust have you looked at having it exit under water?

[Simpo Two]

XJSJohn said:

Remember, when fitting the sound insulation its not just teh underside of the cockpit sole that you need to be insulating, but the sides of the hull and bulkhead within the engine compartment, and sides of fuel tanks etc -

for the exhaust have you looked at having it exit under water?

Thanks John - the engine bay has large compartments on either side which are partly insulated with about an inch of black foam, but whether it's the right sort or sufficient I can't know. Some boats do have the exhaust exiting underwater but a 40hp Yanmar and a 3" pipe makes a surprising amount of gas - it would look like a giant fart! - but more importantly I'd be unable to check the cooling water exit, and that's not a risk I'd be happy taking. Unless I go for the separator mentioned above. What I'd really like is for an expert to look at it and tell me what's needed, rather than me just guessing and spending £££ on stuff that doesn't work!

[XJSJohn]

is the foam on the engine side of the bulkhead or the other side? Needs to be inside the engine compartment to "absorb" the sound too.

Fair comment on underwater pipes, its more hassle to add a telltail.

[Simpo Two]

Yep, on each side of the engine and the forward bulkhead too. Shetland say they use Yanmar as they're quieter than Vetus - god knows what a Vetus sounds like!

[hidetheelephants]

The 1" black foam is cheap stuff boatbuilders fit; it's better than nothing, but not by much. Multilayer stuff with high and low density layers and ideally a thermal layer is a lot better.

[MOTORVATOR]

Taking all mine out Simpo. Just done a journey to Guernsey and back and couldn't hear the Detroits for the incessant nattering coming from the wife.

So two options open to you. Have the old sound deadening material or the wife whichever suits.