anyone know how to quiet a two stroke.

[Ranchero50]

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]

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

 

[CedarRiverScooter]

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.

 

[PSG-1]

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.

 

[CedarRiverScooter]

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

 

[PSG-1]

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.

 

[amk]

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]

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]

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.

 

[JL8Jeff]

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.

 

[PSG-1]

Cedar River Scooter, if it was me, I would simply build a wider box that would fit over the existing box and bolt it in place with some type of bracket, or directly overlapped and bolted.

With the add-on box being about 3-4 inches wider on each side of your existing one, you should have more than enough clearance. Then, install your exhaust flange into the top side of that box, and install baffles.

 

[Robert Smith]

anyone got any tips on how to quiet the noise from these jet ski engines were putting in. My 760 is loud enough I now need to wear ear plugs if I'm going to run wot for a hour. Im seriously considering spray foaming my resonator box and exhaust lines. Any other ideas?

Inject some water into exhaust flow on the downward side of muffs(keeps wTer from backing into motor) and buy some (real) sound insulation for compartment