Spiker 1200hp 460

[rschap1]

mufflers?

Too bad about the neighbor

[Coolerman]

Your neighbor has complained about the noise?

Put mufflers on the boat,

BUT....

Make sure to have the 1100hp track on your Ipod turned up to make up for it......

[spiker]

The neighbor 3 doors down he is in his late 70's, causes headaches for the whole subdivision and we only have 7 houses in it. The two on either side of me go with us sometimes and love it, will only put the mufflers if we get hassled, otherwise I was not bothered last year and we intentionally went fairly close to a few patrol boats.

[Ratickle]

Is there a decibel level maximum where you're at? I talked with the guys at CMI at the Miami Show about your problem and they said other than turndowns, there is nothing they know of that would not restrict flow and HP for a marine muffler on a 1200 HP engine.

[spiker]

86 or 87 somewhere in there

turn downs would take some doing, as the exhaust is does not go straight out the back the two center pipes are crossed with the staggered motors

[Ratickle]

Iowa Mufflers and Noise Limits


The exhaust of every internal combustion engine on any powerboat must be effectively muffled by equipment constructed and in use to reasonably muffle vessel noise.

Powerboats must meet the following SAE sound level tests.
•Stationary sound level test: Engines manufactured before January 1, 1993, must not exceed a noise level of 90 dBA. Engines manufactured on or after January 1, 1993, must not exceed a noise level of 88 dBA.
•Shoreline sound level test: Engines must not exceed a noise level of 75 dBA.

All muffling devices used on powerboats must be in good working order and in constant operation to prevent excessive or unusual noise.

The use of cutouts is prohibited, except for vessels competing in an authorized marine event.

[Ratickle]

88 is tough. It does not say which SAE measurement. I'm assuming 3' behind and 3' above, SAE J2005 for the stationary and SAE J1970 for shore measurements.

Are you injecting water into the exhaust by the tails?

[Ratickle]

Do you have a picture of the transom? Steering was the biggest thing in the way on mine for downturns.

[spiker]

I will look for a picture

[endeavor1]

Do you have a picture of the transom? Steering was the biggest thing in the way on mine for downturns.

Got any extra turn downs or pix of yours? My motors Dyno this weekend then back in they go. BBlades is finishing up the props now.

[Ratickle]

Mine go through the offset behind the notch. Look at thia thread for some good pics.

http://seriousoffshore.com/forums/showthread.php?t=2529

[spiker]

Do you have a picture of the transom? Steering was the biggest thing in the way on mine for downturns.

Have not forgot, have not been to make to the lake since mid February

[spiker]

Do you have a picture of the transom? Steering was the biggest thing in the way on mine for downturns.

Picture of transom

[Ratickle]

Looking at the pic, I definitely think it is doable. Those appear to be 4"?

Anyway, go to the thread link I put in post 331, look at Bradz photo of his downturns in post 29 on there for what your outside two should look like. As he says, he blew up motors trying to make mufflers work on high horsepower motors. Because of your drive configuration, you don't have the room to do like Seadated posted in #34 on that thread. However, it looks as if you can do a single downturn in the center that would be the oval version of a single 6" tube. A 4" diameter circle has 12.6" of volume. A 6" diameter circle has 28.3" of volume. So, a single 6" stainless tube downturn, smashed oval so it sticks out the same amount from the transom as the outside 4" downturns, should be perfect. The collector to go from two 4" to a single oval 6" should not be that hard to do. I would also inject water into the tubes about halfway down. That will keep it tolerable when you're not going slow enough to have the tips underwater.

[spiker]

They are 5"

[Ratickle]

Okay. A 5" diameter circle has 19.6" of area. Two into a 6" won't be enough volume. 7" would have 38.5" of area, which is great. But, no one I know of makes 7" diameter stainless tubing. It jumps to 8".

Personally, I would start on the project. The last thing you want is to get caught and grounded until it can be quieted.

How much room is there between the drives? To make a 7" oval, you would need about 9 to 10 inches of room I think.

Send pics with dimensions to Chris at CMI and see what he thinks. email cmorth@custommarine.com

[Coolerman]

You could find a fab shop with small plate roll to roll form some thin wall stainless to 7" or whatever size you want. It wouldn't be a perfect radius, but position the weld seem towards the transom and polish it.

[Ratickle]

Does it sound like a good plan? Or is there something else that would be better?

[spiker]

Trying out something a little different, will be putting them on this weekend and will report back. I have been by a few WP and they have not chased me down yet. I have one WP who is hanging by the house and waiting, the wife used our binoculars to see him looking over at us last Saturday

[fund razor]

Please do report back. I switched to dry exhaust and am getting dirty looks. Thinking about downturns or clamp-ons. Just have straight pipes with flappers.