Please note this thread has been inactive for 90 days. For the best results, please start a new thread.
Results 1 to 18 of 18
  1. #1

    Default Outboard sound insulation

    Is it worth it for me to put sound insulation on the inside of my Force 85hp outboard engine cowling? From all the old adhesive left, it looks like it had some at some point in the past. Will I notice any difference in the sound level? Is it too risky in case some bits fall off in the future and get sucked into the carbs? Will it restrict airflow around the engine?

    Thanks,

    Pete
    Pete
    16 ft. Ebko
    85 hp Force
    Fort Worth, TX

  2. #2
    Moderator Bob_VT's Avatar
    Join Date
    May 2001
    Location
    West Rutland, Vermont, United States
    Posts
    24,383

    Default Re: Outboard sound insulation

    All 2 stroke outboards are loud..... depends on the use of the boat. If you are fishing I would not bother. If you are trying to hold a conversation with people and you do much cruising around it may be worth a shot ....but do not expect miracles.

    Are you running the silencer boxes over the carbs now? I have seen many people who just do not re-install them and yes the motor is even louder. Factory insulation will not restrict your airflow but the sun beating down on the cover will loosen it pretty fast.
    This is a great link to boat specifications http://boatspecs.iboats.com/
    Please, shop iboats first!!


  3. #3

    Default Re: Outboard sound insulation

    Yes, I have the boxes over the carbs. Thanks.
    Pete
    16 ft. Ebko
    85 hp Force
    Fort Worth, TX

  4. #4
    Supreme Mariner
    Join Date
    Mar 2004
    Location
    On Barnegat Bay, NJ
    Posts
    17,582

    Default Re: Outboard sound insulation

    I would think that installing new insulation would be a good idea, if it is not too expensive. You might consider the foil-backed self adhesive insulatation used on heating ducts. A second choice is that bubble wrap stuff made from Mylar.

  5. #5
    Supreme Mariner Frank Acampora's Avatar
    Join Date
    Jan 2007
    Location
    Southeastern Pa.
    Posts
    10,293

    Default Re: Outboard sound insulation

    The original sound deadening was a black open cell foam. It tended to get crumbly with age, break up, and clog the carbs, so most pre-Merc. Force engines will have it removed.

    Any oil resistant sound deadenig insulation will help some with the noise but don't expect miracles. The main air intake is under the steering snout and a good amount of noise will come from there no matter what you do.

    The air box in front of the carbs does nothing to dampen sound. Its function is to capture "spit back" from the carbs and recycle it to the intake manifold.

  6. #6
    Lieutenant Junior Grade pecheux's Avatar
    Join Date
    Jun 2006
    Location
    Boisbriand, QC, Canada
    Posts
    1,141

    Default Re: Outboard sound insulation

    I find that my 15 hp Force (1997) is louder than any other OB that I ve seen yet. I like the idea of using the foil backed insultation as per Chris1956 suggestion. But I do wonder if there is enough room between the cowling and the motor itself ? Anyone knows the clearance space ?

    Tx
    a bad day fishing is better than a good day at work ..

  7. #7
    Chief Petty Officer ddrieck's Avatar
    Join Date
    Jul 2007
    Location
    Casper, Wyoming
    Posts
    584

    Default Re: Outboard sound insulation

    I installed the sound dampening material they use on surfaces when they install those high dollar car audio systems. I believe it is called Dyna-Mat. I got mine from Best Buy but most car or home audio dealer will have it in some form or another. That stuff works awesome at reducing the sound level under the cowl on my 1976 85hp Johnson V-4. Its about 1/8'' to 1/4'' thick and has a self adhesive back. The stuff I installed has not even come close to releasing from the cowl due to heat from the sun and motor. However, be warned, it is expensive.
    Regards,

    ''Fish Me Gone''



    Democracy will cease to exist when you take away from those who are willing to work and give it to those who are not......Thomas Jefferson





    Find out how you can help prevent the spread of Zebra mussels.
    http://wgfd.wyo.gov/web2011/fishing-1000206.aspx

  8. #8
    Lieutenant Junior Grade pecheux's Avatar
    Join Date
    Jun 2006
    Location
    Boisbriand, QC, Canada
    Posts
    1,141

    Smile Re: Outboard sound insulation

    Quote Originally Posted by ddrieck View Post
    I installed the sound dampening material they use on surfaces when they install those high dollar car audio systems. I believe it is called Dyna-Mat. I got mine from Best Buy but most car or home audio dealer will have it in some form or another. That stuff works awesome at reducing the sound level under the cowl on my 1976 85hp Johnson V-4. Its about 1/8'' to 1/4'' thick and has a self adhesive back. The stuff I installed has not even come close to releasing from the cowl due to heat from the sun and motor. However, be warned, it is expensive.
    Sounds like a plan ... thank you
    a bad day fishing is better than a good day at work ..

  9. #9
    Lieutenant Junior Grade pecheux's Avatar
    Join Date
    Jun 2006
    Location
    Boisbriand, QC, Canada
    Posts
    1,141

    Thumbs down Re: Outboard sound insulation

    Quote Originally Posted by Frank Acampora View Post
    The original sound deadening was a black open cell foam. It tended to get crumbly with age, break up, and clog the carbs, so most pre-Merc. Force engines will have it removed.

    Any oil resistant sound deadenig insulation will help some with the noise but don't expect miracles. The main air intake is under the steering snout and a good amount of noise will come from there no matter what you do.

    The air box in front of the carbs does nothing to dampen sound. Its function is to capture "spit back" from the carbs and recycle it to the intake manifold.
    Hi Frank, On my small 15 hp Force kicker there is nothing in front of the carburator air intake ... just an air sucking hole in oposition to my Johnson that has some sort of plastic cover that allows indirect air breathing. Since I plan to use sound barrier material would it be a good idea to have some sort of screen covering the air intake hole to prevent any foreigh material to get inside the carburator ??? would it prevent the motor from operating properly ? TX
    a bad day fishing is better than a good day at work ..

  10. #10
    Supreme Mariner Frank Acampora's Avatar
    Join Date
    Jan 2007
    Location
    Southeastern Pa.
    Posts
    10,293

    Default Re: Outboard sound insulation

    That's one reason Force engines are cheaper than OMC.

    A LONG time ago (on a planet in a different solar system--or some such, been a long time since I saw the movie) 1950s OMC engines had a perforated screen in front of the carb on the two cylinder engines. Older Mercs used a plastic grate in front of the carbs.

    If you use a big enough hunk of screening, massive enough to resist corrosion and crumbling that goes with it or stainless screening, with a high percentage of open space versus wire, the engine should run very happily.

    When in doubt, measure the venturi diameter. Venturi is the narrow part inside the carb not the outer opening. Area = pi R squared. 1/2 diameter times 1/2 diameter times 3.1416 is the area, let the screen open area be equal to at least a MINIMUM of 10% more and greater is better.

  11. #11
    Lieutenant Junior Grade pecheux's Avatar
    Join Date
    Jun 2006
    Location
    Boisbriand, QC, Canada
    Posts
    1,141

    Default Re: Outboard sound insulation

    Got it ... thank you Frank. now I need to do is find something that will fit with those specs in mind. LOL Now that you've mentioned it I do remember the black plastic piece that was mounted on the Merc OB's .... rather big spaced screen type ...
    a bad day fishing is better than a good day at work ..

  12. #12
    Lieutenant Junior Grade pecheux's Avatar
    Join Date
    Jun 2006
    Location
    Boisbriand, QC, Canada
    Posts
    1,141

    Default Re: Outboard sound insulation

    Quote Originally Posted by Bob_VT View Post
    All 2 stroke outboards are loud..... depends on the use of the boat. If you are fishing I would not bother. If you are trying to hold a conversation with people and you do much cruising around it may be worth a shot ....but do not expect miracles.

    Are you running the silencer boxes over the carbs now? I have seen many people who just do not re-install them and yes the motor is even louder. Factory insulation will not restrict your airflow but the sun beating down on the cover will loosen it pretty fast.
    I am curious ... how can silencer boxes make the engine louder ?? May I ask just where is the sound coming from on a small OB ??
    a bad day fishing is better than a good day at work ..

  13. #13
    Chief Petty Officer ddrieck's Avatar
    Join Date
    Jul 2007
    Location
    Casper, Wyoming
    Posts
    584

    Default Re: Outboard sound insulation

    Quote Originally Posted by pecheux View Post
    I am curious ... how can silencer boxes make the engine louder ?? May I ask just where is the sound coming from on a small OB ??
    On a older 2 stroke engine there is always a certain amount of back flow (fogging) that will come out of the carbs. With this also comes the exhaust note of the engine. This is caused by that very brief moment when the piston is in between the intake port and the exhaust port.

    Therefore, a 2 stroke will have a silencer box installed over the carbs to deaden the noise coming out of the carbs.
    Regards,

    ''Fish Me Gone''



    Democracy will cease to exist when you take away from those who are willing to work and give it to those who are not......Thomas Jefferson





    Find out how you can help prevent the spread of Zebra mussels.
    http://wgfd.wyo.gov/web2011/fishing-1000206.aspx

  14. #14
    Lieutenant Junior Grade pecheux's Avatar
    Join Date
    Jun 2006
    Location
    Boisbriand, QC, Canada
    Posts
    1,141

    Default Re: Outboard sound insulation

    Quote Originally Posted by ddrieck View Post
    On a older 2 stroke engine there is always a certain amount of back flow (fogging) that will come out of the carbs. With this also comes the exhaust note of the engine. This is caused by that very brief moment when the piston is in between the intake port and the exhaust port.

    Therefore, a 2 stroke will have a silencer box installed over the carbs to deaden the noise coming out of the carbs.
    Thank you for the info. Is this silencer box a universal part or per OB specs ? I have a 1997 15 hp Force and would like to install one of these silencer.

    Which brings another question to mind ... the cowling seems air-thight so where does the carb pick up the air it needs ?

    Have a great day
    a bad day fishing is better than a good day at work ..

  15. #15
    Lieutenant Junior Grade pecheux's Avatar
    Join Date
    Jun 2006
    Location
    Boisbriand, QC, Canada
    Posts
    1,141

    Default Re: Outboard sound insulation

    Quote Originally Posted by ddrieck View Post
    I installed the sound dampening material they use on surfaces when they install those high dollar car audio systems. I believe it is called Dyna-Mat. I got mine from Best Buy but most car or home audio dealer will have it in some form or another. That stuff works awesome at reducing the sound level under the cowl on my 1976 85hp Johnson V-4. Its about 1/8'' to 1/4'' thick and has a self adhesive back. The stuff I installed has not even come close to releasing from the cowl due to heat from the sun and motor. However, be warned, it is expensive.
    Hi, showed up at Best Buy and they had no idea what the Dyna Mat product was .... any other big stores you could suggest ? Tx
    a bad day fishing is better than a good day at work ..

  16. #16
    Lieutenant Junior Grade pecheux's Avatar
    Join Date
    Jun 2006
    Location
    Boisbriand, QC, Canada
    Posts
    1,141

    Default Re: Outboard sound insulation

    Quote Originally Posted by pecheux View Post
    Hi, showed up at Best Buy and they had no idea what the Dyna Mat product was .... any other big stores you could suggest ? Tx
    A clerk from Home Depot guided me back to Best Buy and advise I would go directly to the car audio dept. ... they had the material ... bought it .. LOL ... will install before spring OB activities ... LOL
    a bad day fishing is better than a good day at work ..

  17. #17
    Lieutenant Junior Grade pecheux's Avatar
    Join Date
    Jun 2006
    Location
    Boisbriand, QC, Canada
    Posts
    1,141

    Default Re: Outboard sound insulation

    Quote Originally Posted by ddrieck View Post
    I installed the sound dampening material they use on surfaces when they install those high dollar car audio systems. I believe it is called Dyna-Mat. I got mine from Best Buy but most car or home audio dealer will have it in some form or another. That stuff works awesome at reducing the sound level under the cowl on my 1976 85hp Johnson V-4. Its about 1/8'' to 1/4'' thick and has a self adhesive back. The stuff I installed has not even come close to releasing from the cowl due to heat from the sun and motor. However, be warned, it is expensive.
    May I ask ... did you cover every inch of the cowl or just the main areas where the dyna mat pieces would fit ? Tx
    a bad day fishing is better than a good day at work ..

  18. #18
    Chief Petty Officer ddrieck's Avatar
    Join Date
    Jul 2007
    Location
    Casper, Wyoming
    Posts
    584

    Default Re: Outboard sound insulation

    I covered the entire inside of the cowl except where the air intake vent was located.
    Regards,

    ''Fish Me Gone''



    Democracy will cease to exist when you take away from those who are willing to work and give it to those who are not......Thomas Jefferson





    Find out how you can help prevent the spread of Zebra mussels.
    http://wgfd.wyo.gov/web2011/fishing-1000206.aspx

Similar Threads

  1. sound like it is missing 85 -85 outboard
    By nottuskram in forum Force & Chrysler Outboards
    Replies: 4
    Last Post: November 17th, 2008, 11:03 PM
  2. Sound of an outboard
    By zach103 in forum Non-Repair Outboard Discussions
    Replies: 14
    Last Post: August 8th, 2008, 03:19 AM
  3. sound dampening / insulation
    By wca_tim in forum Boat Restoration, Building, and Hull Repair
    Replies: 19
    Last Post: April 24th, 2008, 01:25 AM
  4. Sound Insulation for Merc Inline 6
    By mmccurry in forum Mercury & Mariner Outboards
    Replies: 6
    Last Post: November 2nd, 2007, 04:34 PM
  5. insulation for outboard motor cover?
    By fsutim in forum Johnson & Evinrude Outboards
    Replies: 8
    Last Post: May 20th, 2004, 02:13 PM
  1. iboats Forum Directory - Over 100,000 forum posts organized by topic