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Old 07-20-2010, 07:57 PM
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Willallison Willallison is offline
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Additional Silencing

Is anyone aware of any additional silencing that can be installed on a sterndrive installation?
In this case a Mercruiser 4.3 MPI
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Old 07-20-2010, 08:59 PM
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What is the source of the engine noise? Is it loud through the underwater prop exhaust discharge? Is it through transom exhaust? Perhaps marine mufflers are an option. They're space hungry though...

How about tight seal around the engine hatch? Gaps introduce ventilation for sure, but they also let much noise through. You've probably already considered both of these..just some ideas from a novice to a professional.

Quite a design company you have there by the way. Graphite is quite a looker!
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Old 07-20-2010, 11:27 PM
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Willallison Willallison is offline
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Thanks for the kind words Mark
There is no source of engine noise at the moment... One of the primary requirements for a design I'm working on at the moment is that the vessel be quiet.
I will, of course, be doing all the things you suggest, external to the engine - insulation etc. But was wondering about products / systems for the donk itself...
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Old 07-21-2010, 09:13 PM
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What do you mean by donk?
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Old 07-21-2010, 10:07 PM
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Sorry - Donk is Australian slang for motor...
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Old 07-22-2010, 06:08 AM
FAST FRED FAST FRED is offline
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Location: Conn in summers , Ortona FL in winter , with big dock & room for O'nite stop .
www.soundown.com/sitemap.htm

A good source of a variety of products.

Remember a box over the engine will need an engineered non reflective path intake duct to feed the unit.


There are also USCG approved thick paints that absorb sound .

The 2 inch thick 2lbs per sq ft lead sheeting 360 deg in engine box is best.

FF
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Old 07-22-2010, 01:31 PM
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There are two basic ways to diminish the noise you hear from an enclosed compartment. One, you line it with absorbent material. Two, you make the noise exit away form you,(an opening). You can combine both.
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Old 07-23-2010, 02:21 AM
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The noise level in passenger cars dropped a few dB when car makers installed a large plastic cover over the engine, mounted on 4 or 5 rubber grommets.
It is common now on all cars except the cheapest.
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Old 07-26-2010, 10:34 PM
powerabout powerabout is offline
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Most of the noise comes from the induction which is not designed to be quiet like a car.
Merc fitted a kit to 454 inboards many years ago. It comprised of a housing that went over the flame arrestor to allow for a hose connection and had a meter of flex hose with an aluminium bell mouth in the end.
It made a huge difference to quieting the induction noise
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