cabin engine noise in 16 & 19 c-dory's

Rather than try to build a soundproof enclosure around the motor, I wonder if a simple rounded baffle would be effective enough?

If the noise reduction would be signifigant just by reflecting the noise aft and away from the cockpit, there may be no need to build an elaborate chamber in which to enshroud the motor.

A sound reflecting baffle, made esthetically pleasing by making it transparent instead of opaque, could perhaps reduce the noise to acceptable levels.

Whether to make it of flat panels or to make it of compound curves would be an interesting study. It might be possible to find an existing plastic windshield off of a motorcycle, ATV, or some other vehicle that would do the job.

The first step, however, would be to experiment with a crude prototype to see if a simple baffle would be effective enough.

Just some thoughts to consider.

Joe.
 
Sea Wolf":3n6zhlvp said:
Rather than try to build a soundproof enclosure around the motor, I wonder if a simple rounded baffle would be effective enough?

If the noise reduction would be signifigant just by reflecting the noise aft and away from the cockpit, there may be no need to build an elaborate chamber in which to enshroud the motor.

A sound reflecting baffle, made esthetically pleasing by making it transparent instead of opaque, could perhaps reduce the noise to acceptable levels.

Whether to make it of flat panels or to make it of compound curves would be an interesting study. It might be possible to find an existing plastic windshield off of a motorcycle, ATV, or some other vehicle that would do the job.

The first step, however, would be to experiment with a crude prototype to see if a simple baffle would be effective enough.

Just some thoughts to consider.

Joe.
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Joe - I am certain it would help because when I put the back of my canvas down, it makes a big difference.

I am leaning towards using an insulating material like this (Dr. Bob pointed me to this product.) I would like to put it inside the power-head cover to the engine, but I am a little concerned about space and airflow. I read comments on the West Marine site of people that have done it and are happy with the results. It comes in half and one-inch thickness and the half-inch stuff may work inside the cover.

The other option would be to build a front cover over the engine using grey or white Kydex then using the insulation in the above link.

Dave T sent me pictures of how he solved his noise problem, but it would not work on my boat because it would interfere with my generator and camper canvas.

My solution has to be a close fit around my engine. It can’t be more than two inches beyond my engine power-head cover. If it is, it will restrict the turning and rising of the engine.
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Dave dlt.gif
 
Interesting project.

Not sure how big of a difference there is between the cowling on your engine and a Honda 75 HP. To keep the look you might be able to insulate the 75hp cowling and slip it over your current engine cowling. If the fit is good the air intake should work the same. If it is doable, that would maintain the original airflow/clearance around the powerhead. I would think two layers of cowling with insulation would be a good noise reducer and maintain a factory look without much artistic effort.
 
Has anyone tried using this Silent Running product?

http://silentcoating.com/sr_1000.html

I read a few reviews of it a while back and it sounds really good. I have no idea how it works in practice though. It is supposed to dissipate acoustic noise as heat. The attractive thing is that you paint it on so it can easily conform to the complex curves of an outboard cowl.
 
ripple - there are many types of paint applications that are suppose to dramatically reduce the noise and vibration. A couple of years ago I tried one that had claims of almost word for word what Silent Running has.

I built a test tank that I could set my engine in while on the boat and run the engine in gear at high RPM’s. I used a sound meter to check the noise inside the cabin before applying the paint, then tested it again after three coats of paint that I applied inside of my engine cover.

It did reduce the sound from one to three db’s, depending on the engine speed. To my ear, I was unable to tell the difference between 85 db and 83 db, so I do not consider it a viable means or noise reduction.

Maybe if you painted the entire deck, splash well and cabin of the boat, it may make a noticeable difference but it is expensive and heavy. I am going my memory but I believe I paid around $100 for the gallon of paint I got which included shipping. The gallon of paint weighed 20 lbs m/l. You would need at least five gallons and maybe more to do the inside of the boat and from my experience, I don’t have much confidence in it.

C-WEED":q5qkttfp said:
Interesting project.

Not sure how big of a difference there is between the cowling on your engine and a Honda 75 HP. To keep the look you might be able to insulate the 75hp cowling and slip it over your current engine cowling. If the fit is good the air intake should work the same. If it is doable, that would maintain the original airflow/clearance around the power head. I would think two layers of cowling with insulation would be a good noise reducer and maintain a factory look without much artistic effort.
Click to expand...
Chris - that is something I had not thought about but I will be looking into it.

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Dave dlt.gif
 
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