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Thread: Sound/Noise Reduction for Sport Jon - Dynamat?

  1. #1

    Default Sound/Noise Reduction for Sport Jon - Dynamat?

    I'm considering changing out the foam in my engine compartment, hood, maybe even going further and attacking the rear of my boat to quiet things down a little. Has anyone used Dynamat? Safe and Sound has a 1/8" thick 36 square foot roll for $220 and I know it won't absorb water and you can double it and/or apply sound foam to it. Some forums in the lower 48 speak highly of it but express caution when it comes to heat. If anyone has worked with this or has done a project with a SJ please post or send me a PM. Thanks.
    "He should have been packing a more powerful have to be a very good shot or very lucky to stop a brown bear with a .357 Magnum." - Rick Sinnott, Alaska Department of Fish and Game biologist after a double attack by a grizzly.

  2. #2
    Join Date
    Jan 2007
    Southwest Alaska


    You could also try lead sheet glued to the motor cover. Then the foam over that.

    If you look into the construction of the Dynamat, it is sorbothane sheet. Which can also be purchased much less expensively when buying wholesale.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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  3. #3
    Member tjm's Avatar
    Join Date
    Jan 2007


    changing the padding in the dog house will not make much difference at all....the key to quieting down the SJ's is to close up ALL of the gaps in the boat....floor, under the dog house, transom, etc.....just plain ol weather stripping will make a much more noticeable sound reduction than dynamat in the dog house alone...
    pull my finger....

  4. #4
    Member Ellamar's Avatar
    Join Date
    Apr 2006


    Rubber Hold Down Thingys.jpgDitto on what TJM said. On my old SportJon I weather stripped all the way around the dog house and added 2 rubber hold down thingys (technical term) to the front of the dog house to hold it down tight. Seemed to me that made a bit of a difference, it's a good place to start.

  5. #5
    Member fullbush's Avatar
    Join Date
    Feb 2010


    Flexalite fire retardant foam is what I'd recommend IF I was recommending anything. Its really light weight and I held a propane torch on it for about a minute and it didn't even heat up. I underlined the "if" part though. The reason for that is cooling and airflow. These newer engines have a computer that regulates fuel/air flow, my friend was all proud of his new insulation job that he toiled the better part of a weekend using about 600.00 worth of foam. About the middle of June he had ripped every piece out of his engine room because he couldn't get his engines started after shutting them down after a hard run due to vapor lock because the fuel that was in his rails would get to hot. This holds true for fuel injected outboards as well. I'm not saying more insulation can't be installed, I'm saying make sure it doesn't affect air intake as well as air circulation around the top of the motor.

    I forgot one thing, be careful of that foil insulation because it conducts electricity. I had another buddy that used it and the glue failed and a piece fell on his starter wire, believe me when I tell you, it wasn't pretty!

  6. #6
    Member breausaw's Avatar
    Join Date
    Oct 2006


    I just got through spraying 5 gallons of Delta-T inside the V birth and cabin of my boat. Condensation has decreased by 98% and now you can almost hear a pin drop at cruising speed. Took me a week to do but well worth the effert.
    07 C-Dory 25 Cruiser

  7. #7


    Toxic Fumes
    On my list is to replace the foam that is coming off the engine cowling. But in this consideration is also the smoke that the material produces if it's burning. Some of the stuff out there end up being very very toxic when on fire. Just one of the other factors to think about before hand, survive the fire and pass out from toxic fumes is not on my list.
    In a fire people die from the smoke not the fire 80% of the time.
    I'ill look into these products

  8. #8

    Default Since the subject was Sound Deading

    Delta~db is a sound dampening, or sound damping, coating for structural and mechanical noise generated through substrates and surfaces. Mascoat

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