Engine soundproofing: observations and questions

In spite of their great weight, paltry output and explosive fuel, the idea of a 'whisper-quiet' auxiliary like the venerable (or infuriatingly temperamental) Stuart Turner, is appealing. Not that my enquiry is leading me towards a purchase, but are any such units still built?

I know diesels are vastly more reliable at sea...presumably because of corrosion to the electrics of petrol engines?

When one reads of U.S. speedboats with thousands of horsepower, they're often petrol engines...is there a robust gasoline-engine design, which defies use for sailboat units? Or, am I looking for a product so rarely requested that the industry gave up on it?

All replies welcomed. I'm genuinely curious. I know laughably little of engines - beyond their noise, which I dislike. :rolleyes:
 
The short answer is that it is relativly easy (and therefore relatively cheap) to achieve a large initial drop in both noise and vibration (say 50%) - thereafter it gets progressivly more complicated and more expensive to reduce N&V. (law of diminishing returns etc). The last few % will cost big bucks indeed.

There are lots of individual areas to attend to, but here are the simple ones that give best return on investment;

(but, as always, there are other considerations to be taken into account :))

1. 'Initial design' - individual boat owners cannot change the basic designs of engines available (at least not in the short term) - but they can choose between designs - and if low N&V is a priority for you, move it up the list of priorities on your purchase criteria.

2. 'Structural mass' (As Tranona and others have said) - a 2" thick ferro cement hull will have better noise absorbtion abilities than a thin ply or grp 'skin' stretched over frames (a drum!).

3. 'Isolation' (the most mis-understood componant). It is true that once design and structure issues have been decided upon, either by the designer or the product purchaser, 'Isolation' becomes the biggest influence that the installer / maintainer can have - and it can make a massive % difference to the end result. But, be careful! (explanation later).

4. 'Suppression'. After the above three items have been attended to, there remains the option usally most adopted by aftermarket owners - 'suppression' i.e. sound absorbing materials and the like.

I'll post later on items 3 & 4 (I've been sailing, it's late on a Sunday evening, and I'm tired:D :)

But before I nod off, I'll leave you with something to ponder;

If you want to achieve virtual silence I can tell you how to do that (in great detail) though I'm no longer active in that field - but is that what you want?

Yes, noise can be infuriating (it's often used as a form of torture) and vibration can destroy machinery - vibration analysis is one of the very best (if not the best) predictors of wear and future failure - and we all know of the countless times a change of 'engine note' has alerted us to an impending problem in time to take action before total failure - so the question is, how much do you want to silence your machinery?

More later, I'm tired - Specifically I'll address the misconceptions surrounding noise isolation - apologies for any spellung mustakes - did I mention that I'm tired!:)
 
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Many US boats still have Atomic 4s fitted, sort of a US equivalent of the Stuart Turner; petrol, 4 cylinder, 4 stroke side valve and about 30hp. Stopped making them in 1984.

Other common petrol inboards are the Dolphin and the Vire; none are in production, but there are specialists who can do rebuilds.
 
penfold said:
Engine compartment air inlets are often overlooked as paths of noise; they should be baffled and the baffle lined with absorption material.

The few times my dad's Stuart Turner P55 worked(it was fairly knackered; the crankcase seals were gone, the magneto worked part-time and ST carbs were carp even when new) it was whisper-quiet and vibration-free except at idle; it was bolted straight on a steel bed and had no flexible coupling. 8hp from something the size and weight of a 2GM20.
Click to expand...

Are you saying that the ST carb sounded a little fishy!:D

In your earlier post are you suggesting that softer mounts help to reduce vibration?
My 3cyl perkins runs quite smoothly and reasonably quiet considering there is only a peice of insulation on the inside of the grp engine cover/companionway steps, but it vibrates considerably at low revs/idle.
C_W
 
Brightwork said:
The short answer is that it is relativly easy (and therefore relatively cheap) to achieve a large initial drop in both noise and vibration (say 50%) - thereafter it gets progressivly more complicated and more expensive to reduce N&V. (law of diminishing returns etc). The last few % will cost big bucks indeed.

There are lots of individual areas to attend to, but here are the simple ones that give best return on investment;

(but, as always, there are other considerations to be taken into account :))

1. 'Initial design' - individual boat owners cannot change the basic designs of engines available (at least not in the short term) - but they can choose between designs - and if low N&V is a priority for you, move it up the list of priorities on your purchase criteria.

2. 'Structural mass' (As Tranona and others have said) - a 2" thick ferro cement hull will have better noise absorbtion abilities than a thin ply or grp 'skin' stretched over frames (a drum!).

3. 'Isolation' (the most mis-understood componant). It is true that once design and structure issues have been decided upon, either by the designer or the product purchaser, 'Isolation' becomes the biggest influence that the installer / maintainer can have - and it can make a massive % difference to the end result. But, be careful! (explanation later).

4. 'Suppression'. After the above three items have been attended to, there remains the option usally most adopted by aftermarket owners - 'suppression' i.e. sound absorbing materials and the like.

I'll post later on items 3 & 4 (I've been sailing, it's late on a Sunday evening, and I'm tired:D :)

But before I nod off, I'll leave you with something to ponder;

If you want to achieve virtual silence I can tell you how to do that (in great detail) though I'm no longer active in that field - but is that what you want?

Yes, noise can be infuriating (it's often used as a form of torture) and vibration can destroy machinery - vibration analysis is one of the very best (if not the best) predictors of wear and future failure - and we all know of the countless times a change of 'engine note' has alerted us to an impending problem in time to take action before total failure - so the question is, how much do you want to silence your machinery?

More later, I'm tired - Specifically I'll address the misconceptions surrounding noise isolation - apologies for any spellung mustakes - did I mention that I'm tired!:)
Click to expand...

Waiting with abathed breath.
Sleep well.
C_W
 
dancrane said:
In spite of their great weight, paltry output and explosive fuel, the idea of a 'whisper-quiet' auxiliary like the venerable (or infuriatingly temperamental) Stuart Turner, is appealing. Not that my enquiry is leading me towards a purchase, but are any such units still built?
Click to expand...

You can still get reconditioned Dolphins. Vire were in production until quite recently. Stuart Turners were available up to about 10 years ago in rebuilt form as there were tons of spares around. However, even the most anti H&S person would not want one. Splendid pieces of engineering from the 1920's, but functionally a nightmare. Open petrol systems that dribble fuel, raw water cooling that kept them either just hot enough to work, or just too cold leading to oiled plugs. Inaccessible magnetos that were a pig to time. You could tell an ST owner by the assortment of plugs he carried around with him and steel fingertips to help change plugs that had been heating on the primus before putting in the engine. The worst thing with mine was that my labrador hated it when I had to start it with the handle - even more than she hated the Seagull.

Changing to a noisy lumpy Yanmar was a revalation - an engine that works when you ask it to, and more importantly only stops if you tell it to, not just because it feels like it.
 
Tranona said:
You can still get reconditioned Dolphins. Vire were in production until quite recently. Stuart Turners were available up to about 10 years ago in rebuilt form as there were tons of spares around. However, even the most anti H&S person would not want one. Splendid pieces of engineering from the 1920's, but functionally a nightmare. Open petrol systems that dribble fuel, raw water cooling that kept them either just hot enough to work, or just too cold leading to oiled plugs. Inaccessible magnetos that were a pig to time. You could tell an ST owner by the assortment of plugs he carried around with him and steel fingertips to help change plugs that had been heating on the primus before putting in the engine. The worst thing with mine was that my labrador hated it when I had to start it with the handle - even more than she hated the Seagull.

Changing to a noisy lumpy Yanmar was a revalation - an engine that works when you ask it to, and more importantly only stops if you tell it to, not just because it feels like it.
Click to expand...

Thanks. Enough said. I'm persuaded!

I'll stick to noise containment, rather than origin-alteration. I had a peep at the Aquadrive website earlier...looks clever, but simple. Nice combination.
 
I have read that STs can be made to behave; the crank seals must be sound, the magneto ditto(or more realistically binned for a 12v coil system) and an Amal or Mikuni carb fitted where the ST horror usually bolts. Even when new those carbs were awful. A bit grandfather's axe, but there you go. Fit an intercooler and you could even reduce oiling up at low revs.
 
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I know this is an old thread.... but hoping someone can help.

I am having trouble trying to find fire-proof engine bay insulation, has anyone here had any luck finding some sort of fire-proof insulation at a reasonable price? I need about 10m x 1m
 
Placing the engine in a box inside the hull was done by Swedish motorboat manufacturer Örrskär in ther stern drive powered 31'

When out looked like this
orrskar_2.jpg


orrskar_1.png


Can't say if or how good this worked, but others use different solutions - then and now.
 
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alt said:
I know this is an old thread.... but hoping someone can help.

I am having trouble trying to find fire-proof engine bay insulation, has anyone here had any luck finding some sort of fire-proof insulation at a reasonable price? I need about 10m x 1m
Click to expand...

www.halyard.eu supply insulation that meets the ISO standard
 
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