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Thread: Mufflers for the 35HP Briggs

  1. #1
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    Mufflers for the 35HP Briggs

    Hello folks,

    I am currently completing a mini airboat project but this is a first airboat experience of any kind for me... At this point I feel I want to reduce the engine noise from the 35 HP Briggs as much as possible (I understand there will still be a propeller noise). So far I've tried it with a pair of those red bullet glasspacks which didn't seem to be much improvement over running without any mufflers at all. So I have a few questions:

    - is there actually a risk in running this motor without mufflers? Burning out valves, etc?
    - is there a preferred muffler choice for this motor?

    My motor is the type that comes without any muffler but I see that there 3 different mufflers listed for other versions of this motor. Is one of the factory mufflers worth looking into?

    I appreciate any advice on this.

    Thanks!

  2. #2
    KWAZY old Southerner... Duane Scarborough's Avatar
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    DC_10,

    Welcome to the forum.

    I'm not familiar with the "red bullet glasspacks" that you mentioned. Are you talking about something like automotive "cherry bombs"? (about 2" inlet/outlet)

    I would not run any engine without mufflers, unless it had a very long exhaust pipe, because of the burning exhaust valves risk.

    Chuck Rackley at Airboat Pros has had a lot of experience with these engines. I suggest that you give him a call.

    Airboat Pros
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    Duane
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  3. #3
    Senior Geezer buster's Avatar
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    DC_10,

    Welcome to the best place around for an airboat builder

    I just wanted to pass along some info that I read in several different places. It is about making a small engine quiet. I don't know this from personal experience, but it does sound right.

    It seems about the cheapest, and probably the easiest way to accomplish that is to use as long an exhaust pipe as you can. So far I never tried it, but I just may on the VW tomcat I'm building now.

    I did however try the opposite method, that is putting a big muffler off of very quiet Ford, and mounted it onto my very noisey 12 hp b&s powered light plant. It did not make much difference. I guess it's time to try the other way now. If you do it, let us know the results.

    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  4. #4
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    I used tractor muffler's from tractor supply. they are light in wight and cheep.Thay are not loud at all and they do put a little back psi on the engine like it need's.

    Steve
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    Last edited by n4wsp; 08-18-2011 at 11:25 AM.

  5. #5
    Administrator Papee's Avatar
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    I second Check with Chuck, he also was experimenting with a cross pipe exhaust for that engine. I ran my briggs without mufflers but I had a few bends in the pipe and they were about 4-5ft in length. I'm not sure that was the best as far as performance.
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  6. #6
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Quote Originally Posted by buster View Post
    I did however try the opposite method, that is putting a big muffler off of very quiet Ford, and mounted it onto my very noisey 12 hp b&s powered light plant. It did not make much difference.

    Dave
    Buster,

    That's kinda' why I was asking about the SIZE of the mufflers. I've seen way over sized mufflers installed on small engines myself. They do change the tone of the noise, but don't seem to do much to reduce the overall noise.

    It's almost like there isn't a muffler there at all. Kinda' like yelling into a big tunnel?

    But Papee is on the right track. I have seen vehicles with VERY long exhaust pipes, that had no muffler at all, or a minimal muffler. Look under an old school bus.

    Chuck can probably steer him in the right direction.

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

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    Hello everyone,

    Thanks for the replies so far!

    Duane, yes, they were the Cherry Bomb mufflers. I heard them referred to as "glasspacks". You can look right through them and it seems most of the sound went right through them as well...

    Dave and Papee, interesting suggestion about very long pipes. Do I need to be concerned about creating the "correct" backpressure for the engine? Or is it not so critical, as long as there is some backpressure?

    I like the idea of an inexpensive tractor muffler like Steve described. The local small engine shop indicated that the factory mufflers for the 35 Briggs would be in the $300 ballpark!! Ouch! On top of that so far they could not give me exact dimensions of that muffler and since it bolts directly onto the motor I would want to be sure that it will fit in the space I have.

    I will definitely want to contact Chuck for advice... I saw his post in the archive that had actual sound measurements for that motor at idle. I might be able to borrow a sound meter for a day and see where I am at.

    Thanks again

    Derek

  8. #8
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Quote Originally Posted by DC_10 View Post
    Hello everyone,

    Thanks for the replies so far!

    Duane, yes, they were the Cherry Bomb mufflers. I heard them referred to as "glasspacks". You can look right through them and it seems most of the sound went right through them as well...

    Dave and Papee, interesting suggestion about very long pipes. Do I need to be concerned about creating the "correct" backpressure for the engine? Or is it not so critical, as long as there is some backpressure?

    I like the idea of an inexpensive tractor muffler like Steve described. The local small engine shop indicated that the factory mufflers for the 35 Briggs would be in the $300 ballpark!! Ouch! On top of that so far they could not give me exact dimensions of that muffler and since it bolts directly onto the motor I would want to be sure that it will fit in the space I have.

    I will definitely want to contact Chuck for advice... I saw his post in the archive that had actual sound measurements for that motor at idle. I might be able to borrow a sound meter for a day and see where I am at.

    Thanks again

    Derek
    DC_10 (Derek),

    Way back, a VERY long time ago, we'd put "Cherry Bombs" or "glass packs" on our hot rods to satisfy the local police officers. They were not very effective as mufflers then, and they probably still are not today. I don't know. But they met the minimal requirement at the time. They WERE loud, and that's all we cared about, then.

    Airboats are NOISY. Face it. The noise comes primarily from 2 sources. The exhaust, which can be quieted somewhat with a decent muffler/exhaust system. and the prop.

    Chuck is right down there in central Florida where there's a battle going on about airboat NOISE. So he CAN help you out there. He is well informed on what's going on.

    Now, in North Carolina, the airboat noise has NOT been an issue, because there's not very many airboats here. And I don't intend to make it an issue.

    So, I've tried to be a good neighbor, by using a good muffler system, AND by using a reduction drive to reduce the prop speed. (reduced prop speed = reduced NOISE)

    I don't know about you, but I'd sure as heck rather spend my time at the boat ramp with onlookers asking questions about the "cool" Mini AirBoat, than dealing with the local law enforcement officers over a noise complaint.

    Some of the guys down in FL insist on running open headers, on high HP direct drive boats. They can be VERY LOUD. Then, they complain about the noise complaints against them.

    Me, I'd rather have a decently quiet boat the doesn't attract much negative attention.

    Maybe I'm just getting old.

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  9. #9
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    Hey Derek, Steve made the right suggestion with the 1.5 inch Mufflers from Tractors Supply that will keep the cost down. The part number should be IH1. They aren't Stainless Steel but they will last a long time. Make your header tube with 1.5 inch tube. You can get a muffler shop to bent it 90 degrees, one for each side. They could be about 12 inches long. You need to find 2 flanges to bolt to the engine and weld the tubes in. We have used continnental GPU flanges, the bolt pattern is the same. If you can't find the parts to make the headers, we make them in SS at $ 80.00 for the set. You need about 3 ft of 1.5 inch flex tube on each side and 4 T bolt clamps. We have al this in SS if that is what you want. We also make the SS mufflers and they are $ 78.00 ea. You would need the ss if you are going to run in salt water. Let me know if i can help you.
    Thanks, Chuck

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    Hi again,

    Duane - In my area there are very few airboats, but I definitely want to be able to reduce the sound, especially when I am passing a kayak etc. So for those situations when propeller speed/sound is already lowered I need an effective exhaust muffler to "sneak by"....

    Chuck, thanks a lot for the info. I am not planning to run on salt water but I really like the quality feel/look of a stainlees exhaust system... How does your custom stainless muffler compare in noise reduction performance to the IH1? I am also thinking that it may be the simplest to get a complete exhaust kit from you - I do have the 90 degree pipe headers but they are not stainless. I will try to call you later today or Monday afternoon regarding that.

    Thanks!

    Derek

  11. #11
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Quote Originally Posted by DC_10 View Post
    Hi again,

    Duane - In my area there are very few airboats, but I definitely want to be able to reduce the sound, especially when I am passing a kayak etc. So for those situations when propeller speed/sound is already lowered I need an effective exhaust muffler to "sneak by"....

    Chuck, thanks a lot for the info. I am not planning to run on salt water but I really like the quality feel/look of a stainlees exhaust system... How does your custom stainless muffler compare in noise reduction performance to the IH1? I am also thinking that it may be the simplest to get a complete exhaust kit from you - I do have the 90 degree pipe headers but they are not stainless. I will try to call you later today or Monday afternoon regarding that.

    Thanks!

    Derek
    DC_10,

    It sounds like we have similar ideas.

    My thought is that at idle speed, or close to it, the boat should be REALLY quiet. And at Wide open throttle, it should still be RELATIVELY quiet. As much as we'd LIKE, there is no such thing as a completely quiet airboat. It's just the nature of the beast.

    One thing we CAN do fairly easily is reduce the exhaust noise. The prop noise is not as easy, but we should do what we can.

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  12. #12
    Senior Geezer buster's Avatar
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    As long as we are talking about prop noise, I thought I would throw this in the mix. I read about a guy that was running a Big carmotor boat that figured he had a very quiet setup.

    I don't remember what he had for an exhaust, but his prop was five superwide blades. I believe he could get all the push he needed with a high reduction setup, without turning the prop very fast. Makes sense, the slower the prop turns, the less noise it makes.

    I don't think anyone makes a similar prop or reduction suitable for a mini airboat though.

    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  13. #13
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Quote Originally Posted by buster View Post
    As long as we are talking about prop noise, I thought I would throw this in the mix. I read about a guy that was running a Big carmotor boat that figured he had a very quiet setup.

    I don't remember what he had for an exhaust, but his prop was five superwide blades. I believe he could get all the push he needed with a high reduction setup, without turning the prop very fast. Makes sense, the slower the prop turns, the less noise it makes.

    I don't think anyone makes a similar prop or reduction suitable for a mini airboat though.

    Dave
    Buster,

    There is a big movement going on in FL to reduce the prop SOUND. They don't like to use the N word.

    There's also a lot of effort being put into reducing the overall SOUND.

    I forget his name, but there's one guy on the SA forum who has a high HP boat, that has done a lot in that direction. He says that he can talk on his cell phone while at cruise speed.

    He's done this with good mufflers, long exhaust pipes, a reduction drive, and a big, relatively slow speed prop.

    We all need to do what we can to reduce the SOUND volume of our toys.

    There's still some head up their butt die-hards down there that still insist on running big engines, with open headers, and big direct drive props. Seems like their mission is to tick off as many people as they can. They are making it hard for everyone else.

    Granted, a high performance boat does need a high performance engine. I'm O.K. with that. However, high performance does not have to be LOUD. We need to be aware that if we tick off our neighbors, they will have the government impose rules that will limit us all.

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  14. #14
    Senior Geezer buster's Avatar
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    Duane,

    I'm all for making the boats as quiet as possible, there is no need to keep asking for trouble. But then, some people may complain about the boats even if they were quieter.

    I remember an incident about a lot of snowmobile noise complaints at night on a certain nearby lake. The snomobilers got together one night when the moon was bright, and ran that night with their lights off. The sheriff took a survey from the residents the next day, and found out no one heard any snowmobiles that night! Seems it was all in their mind when they saw the headlights bobbing around.

    Also, I think the guy on the SA forum you mentioned is the same guy I was talking about. He had a picture of the rear of his boat, and the five blade prop is HUGH! I bet he has close to five grand in the prop alone.

    If you can run that quiet, maybe you can even sneak up on the wildlife ,..... not that I would ever do such a thing

    Dave
    Last edited by buster; 08-21-2011 at 09:49 AM. Reason: spelling and punction
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  15. #15
    Quote Originally Posted by DC_10 View Post
    Hello folks,

    I am currently completing a mini airboat project but this is a first airboat experience of any kind for me... At this point I feel I want to reduce the engine noise from the 35 HP Briggs as much as possible (I understand there will still be a propeller noise). So far I've tried it with a pair of those red bullet glasspacks which didn't seem to be much improvement over running without any mufflers at all. So I have a few questions:

    - is there actually a risk in running this motor without mufflers? Burning out valves, etc?
    - is there a preferred muffler choice for this motor?

    My motor is the type that comes without any muffler but I see that there 3 different mufflers listed for other versions of this motor. Is one of the factory mufflers worth looking into?

    I appreciate any advice on this.

    Thanks!
    Hello

    I run a 35 Briggs on a hovercraft over hear in the UK. I have used regular car mufflers to good effect, my local specialist exhaust shop made one up for me in stainless, I asked them for a "quiet" system and the exhaust can't be heard when underway. Incidentally its also siamesed with a 13hp Briggs lift engine! Sounds odd but works nicely.

    Prior to the stainless set-up I bought a random exhaust from a small VW, cut it and rewelded to suit the Briggs, that was also very quiet (but only lasted one season as I run in salt water usually)

    Other people use mufflers from motorbikes over here - stainless ones can be bought cheaply from ebay because all the bikers over here junk them for aftermarket "high performance" mufflers.

    Ian

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