anyone know how to quiet a two stroke.

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PSG-1
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anyone know how to quiet a two stroke.

Post by PSG-1 » 12 Jun 2015, 22:50

CedarRiver, does your boat have a rear platform? If not, adding one will help quiet it down a little bit.

Also, if your exhaust exits right out the transom, you might consider adding some type of chute that goes over the exhaust outlet (picture something like a chute that covers a typical household dryer duct on the outside of the house) This will direct sound toward the water that's rushing from under the edge of the transom, instead of straight out the back of the boat. You can make the chute with the bottom edge as low as you want (the lower the better), just as long as it's about an inch or two above the bottom edge of the boat, so you don't force water into the exhaust.

I ran a setup like this on my boat when it had the 2 stroke engine, and it definitely helped.
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Ranchero50
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anyone know how to quiet a two stroke.

Post by Ranchero50 » 13 Jun 2015, 07:28

CedarRiverScooter wrote:This is a dissatisfier for me also. Been going on hour+ rides, & my ears are ringing when I get back. I tried to add the skirt, but the polaris pump tunnel has obstructions making this impractical. I put a rubber 'flap' on the EXH outlet, but I think it is limiting power more than noise.

My immediate plan is to use earplugs.

Long term, I would love to find a 4 stroke engine, I think it would be easier to muffle without losing power. Been using 4 gallons of gas per hour, btw, would like to reduce that too.

So far I have run up on a gravel shoal, hit a rock & a log, - no damage to the boat!

It's a blast . . .
What speed are you only using 4 gph?

This is my current exhaust setup. You can see the old discharge above the pump and it was very loud there. With the new version on the pod the exhaust is pretty quiet until I'm running hard because the port is under water. I am running the stock water muffler as well. You can get an idea from my goofing off videos of how it sounds.
Image

As said above, a lot of my noise is from the decking vibrating at speed. I put some fuzzy velcro at the hatch openings to quiet them down. Eventually I'll install the carpet (it's only been sitting in the rafters for six years waiting) and hope it quiets everything down.

CedarRiverScooter
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anyone know how to quiet a two stroke.

Post by CedarRiverScooter » 13 Jun 2015, 12:42

Thanks Ranchero for the picture. Good idea on the underwater exhaust. I have an idea on how I can try that out without cutting a hole (running a radiator hose down the outside of the transom). If it pans out, then I will make it permanent.

I have been cruising about 25 MPH, & usually use 4 gallons on the hour trip (up to the dam & back). It uses 6 + gallons if I go above 30 MPH for the same trip. The pump must lose efficiency at the higher output.

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brianb2247
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anyone know how to quiet a two stroke.

Post by brianb2247 » 15 Jun 2015, 20:28

some skis come with water boxes that dont have the water line connection on them ,typically they are louder than the ones that do this can be a mod upgrade to quiet down yours , the other thing you can do is make an air tight engine lid over your engine then make an opening on the far front corner of it to draft fresh air across the engine and in through the intake i used a 3 inch blower cover. my engine cover is welded in and sealed with poly seam sealer from lowes and to quiet it more i rolled the behr deckover textured paint over it two coats (with a special roller) really took the pinging noise away from traveling through the aluminum. [-X do not use the restore deck paint its sand based and will burn you up in the summer heat

CedarRiverScooter
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anyone know how to quiet a two stroke.

Post by CedarRiverScooter » 17 Jun 2015, 19:20

Well, I got some flexible exhaust pipe & was able to route the exhaust over the transom & down underwater. $10 total cost so far. It sticks down about an inch below hull. Made quite a difference in noise level, but you guys are right, the exh is only half the noise source. Now I can hear all the rattles, etc. The flex pipe is temporary, hopefully will come up with more elegant design next winter.

I was concerned I would get a hydrolock situation upon shutdown/restart but that didn't happen.

The only negative consequence is spray up onto the transom. Next I am going to make a shoe to hold the spray down. I'll take a picture once I get that done.

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Ranchero50
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anyone know how to quiet a two stroke.

Post by Ranchero50 » 17 Jun 2015, 21:17

I would keep it an inch above the hull bottom and I doubt you'll have much spray and about the same noise level.

Capt1972
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anyone know how to quiet a two stroke.

Post by Capt1972 » 17 Jun 2015, 21:33

put a U in the pipe and you wont get hydrolocked. Like a trap under your sink but reversed.

CedarRiverScooter
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anyone know how to quiet a two stroke.

Post by CedarRiverScooter » 29 Jun 2015, 22:12

Been working on this, with limited success.

I installed underwater exhaust & lined the engine compartment with carpet & foam. In fact have covered the top of the engine with a foam pad (I have good air scuppers, so engine is staying cool). The engine hood fits pretty well, lays on the deck carpet.

I have a sound meter & with all this I'm still at 97 dBA wot.

The good news - only 80db at idle.

My bad, didn't take readings on the original configuration, but it was louder for sure.

Looks like earplugs are going to be the plan going forward.
dutchboat 004.JPG

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PSG-1
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anyone know how to quiet a two stroke.

Post by PSG-1 » 30 Jun 2015, 13:15

I'm sure the foam probably had an effect on the sound.
If it were me, I'd box in the jet pump, carry that outlet into the top side of the box, and then add rubber skirting around the pump. Similar to the setup on my boat.
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http://www.tinboats.net/forum/viewtopic ... 21&t=22023


Fishing, jet skiing, target shooting, jet-boating, and even a little oyster harvesting with Larry The Cable Guy.
Watch it all right here:

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CedarRiverScooter
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anyone know how to quiet a two stroke.

Post by CedarRiverScooter » 31 Jul 2015, 08:36

I think this might be going the wrong way!

At least you could put the fire out by doing donuts . . .

https://www.youtube.com/watch?t=10&v=uyZIZPua5uI

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PSG-1
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Location: South Carolina (redneck riviera)

anyone know how to quiet a two stroke.

Post by PSG-1 » 31 Jul 2015, 14:35

Well at least your 2 stroke engine isn't THAT loud! Even as cool as that "jet" boat looks, I don't really see the fun in having to wear flight deck earmuffs to be able to go for a boat ride.
ALUMA-JET project:
http://www.tinboats.net/forum/viewtopic ... 21&t=22023


Fishing, jet skiing, target shooting, jet-boating, and even a little oyster harvesting with Larry The Cable Guy.
Watch it all right here:

http://www.youtube.com/user/HKPSG1Shooter?feature=mhee

amk
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anyone know how to quiet a two stroke.

Post by amk » 03 Aug 2015, 16:38

there is not part of the back side of my boat that is ever under water when im on a plane so my exhaust will always be above water unless I cut a hole in the bottom and route it out like that so ya ear plugs will be my solution.

CedarRiverScooter
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anyone know how to quiet a two stroke.

Post by CedarRiverScooter » 04 Aug 2015, 21:29

I had the exhaust sticking about 1/2 inch under hull & even had a bevel cut for exhaust suction. Engine didn't perform the same, would have flat spots in throttle response, but not all the time. I gave up on the concept & bought a box of ear plugs. Funny, none of my passengers think it excessively loud, so guess it's just me.

CedarRiverScooter
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anyone know how to quiet a two stroke.

Post by CedarRiverScooter » 04 Aug 2015, 21:31

I had the exhaust sticking about 1/2 inch under hull & even had a bevel cut for exhaust suction. Engine didn't perform the same, would have flat spots in throttle response, but not all the time. I gave up on the concept & bought a box of ear plugs. Funny, none of my passengers think it excessively loud, so guess it's just me.

PSG, I looked a skirting but the tunnel is too tight with the steering & reverse cables, so didn't proceed with that.

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JL8Jeff
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anyone know how to quiet a two stroke.

Post by JL8Jeff » 05 Aug 2015, 11:59

You may want to search around the web for Jetcraft, Westcoast, Coffman, TDR waterboxes and silencers. They all make a large variety of exhaust parts for pwc's so you might find something you can fab up. I would suggest something that has a water fitting because that helps knock down the noise better. They also could probably fab up a silencer to your specs if you can determine how much room you have. My sprint boat has some mufflers that really keep down the noise but they are a little fat so you might not have room for one.
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2001 Lowe Roughneck 1652 VT with Merc 60/45 jet 2 stroke

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