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Engine Box and Sound Insulation


Kennneee
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Hi Guys


My Yamaha 90 is reasonably quiet for an outboard motor. I would like to reduce the noise further and am building a box that will cover the engine well and the outboard as far back as the transom. Wondering if anybody has any experience with something like this and how effective has it been? Need recommendations on sound insulation that would be waterproof as well.
Thanks.
Ken

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I used foam/foil soundproofing material available through West Marine or Defender or similar marine stores. The material is 1.5 or 2 inches thick. My installation was around the engine on an I/O, so totally enclosed.

 

The noise reduction was significant and worthwhile, but not as quiet as I hoped. My boat is also made of plywood, so the whole thing is a sound board. The best place to ride is in the bow where the dash and windshield block the sound.

 

The foam in soundproofing is open cell. It absorbs sound, but also water. I don’t know how effective it is when wet. The foam is also flame retardant to a modest degree.

 

You might first fashion a shell around your motor well to see if that helps. When the boat is at speed remove the shell to hear the difference in sound levels. Then proceed to add foam.

 

Good luck. I admire your work.

 

 

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Reacher - Thanks for the input. I need to find an insulation that can withstand the weather. When the motor is tilted up the inside of the box will be the outside. Not sure if this is a fools errand. Won’t be my first.

Ken

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I built a sound proofish enclosure for a deisel generator on a Little Harbor 53.  The biggest design problem, and you have the same issue, is air supply to the engine. I built in a baffle lined with lead faced foam. It will be interesting to see what you come up with.

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Dave- What I am building is a three sided cover. The aft end will be open. Certainly not as quiet as a 4 sided box would be. I don’t expect miracles but hoping for some sound reduction. In the pilot house the engine noise isn’t bad. Sitting outside when we are under weigh is when the noise is annoying. I am hoping the curved top of the box will act a little like a megaphone in reverse reflecting more of the sound behind the boat.

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Hi ken,

 

Here are a couple of pictures from my engine box.  I did use some sound deadening paint on the inside.  Don't know if that actually worked.  The whole assembly does cut down the sound.

The top cover and the frontcover can lift off easily to access the engine.  

The center section hinges up by means of a little wheel that rests on top of the engine. I should have made the hinged part wider, the engine needs to be fairly straight when raising it up.

 

I do need to modify the hinged part.  The engine can't go up high enough to keep it completely out of the water.  After we moved I keep the boat in a slip end the lower unit is one barnacle mess.

Really like how Rosie turned out and glad you got to use her.

Egbert

 

Transom Name.jpg

Cockpit Table.jpg

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Egbert- A lot of your ideas have been helpful to me during my build. Your engine cover in one of them. Thanks! Did you move to another area?

I installed trim tabs on Rosie and they have been more valuable then I expected. When I installed them I put a coat of epoxy and then some bottom paint (hydrocoat) on them. The paint didn’t adhere well and I had some growth on the tabs when we hauled her out. I am going to try some of Pettit’s Barnacle Barrier this year. Perhaps it will help with your barnacle issue.

Ken

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We moved to a bit more populated area in a little condo that came with a boat slip.  Right at the mouth of the York River in Virginia.  Bought also another property nearby to put up a workshop.  Waiting on a concrete slab to be poured, but it keeps on raining and then it rains again. 

 

I should have known better than relying on the Hydrocoat that was applied in 2014.   Will have to do a lot of scraping and sanding. I might also look at the Barnacle Barrier.

 

Henry told me you had trouble with the gas tank vent spitting back.  I got lucky and can fill the boat without it spitting gas.  What does happen when the tank is full and heats up gas is leaking out of the vent.  Wonder if one of those devices you were looking at would help with that.  Can you post a link to that discussion?

Egbert

 

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Egbert- Building a new shop is daunting but fun. Hope you get to enjoy the project when it stops raining.
The Hydrocoat that I applied 2 years ago is working well. It wasn’t the fault of the Hydrocoat that it didn’t adhere to the trim tabs. I have ordered some of the Barnacle Barrier and hope that does the job. I will overcoat it with Hydrocoat. Have you tried the Hydrocoat Eco? Maybe someone reading this has and can comment. Thinking of using that next time I paint the bottom.
My venting problem was not unique. When I filled the tank the vent would spew fuel before I had a chance to stop the flow. If the tank was filled very high and the weather warmed, fuel would seep out of the vent. Not a lot but enough to make a mess. I added the Attwood parts shown in the link below. One of my concerns was that my vent did not have a high loop and there was a chance water could enter the vent and contaminate the fuel. The Vent P-Trap took care of that. The other part is a fuel line surge protector. I believe it has a floating ball that closes off the vent when a surge of fuel causes it to float and block the exit. The 2 parts described seem to work as designed. Sometimes a very small quantity of fuel will come out of the vent when filling but a fraction of of what happened before. I still have to watch for a surge out of the filler but if I am careful it isn’t a problem. One problem they didn’t solve is a slow weep of fuel out of a warming full tank. If it is a slow weep the floating ball doesn’t close. I solved that problem with the vent cover I fabricated. It covers the vent and still allows air flow. I hang a plastic container off of the piece of hose attached to it when I fill up and when leaving the boat with a full tank on a hot day. Works great. 
One of the links below is a long thread on the Glacier Boats forum for a beautifully built Great Alaskan 28. The builder is very knowledgeable and particular. A lot of things discussed including his venting problems. You will have to read a bit to find the parts about venting interspersed with other topics.
Hope that helps. Let us know how these things work if you decide to use them. Pics of the shop would be great as well. It it is anything like your BJ, it will be impressive.
Ken
 
 

 

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Thanks for the info and links Ken.  The shop will be a Carolina Carport barn style metal building.  No time to build myself from sticks, would take way too long.  Covered the area in plastic today to hopefully keep it dry from the rain tonight.

 

Egbert

 

 

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