Re: In Line Silencers
Don't mean to argue, but the cheaper ones actually do make a significant difference in sound level - they're more like a plug in terms of what they do to backpressure, but on a stock 305 shouldn't hurt performance much if any. The ones that emi makes or hardin are very similar. another relatively inexpensive thing that can help is adding rubber flaps on the tops if you don't have them. Also, turn downs on the tips direct the sound downward and make a big difference in what you can hear in the boat.
The reason that a well designed boat "silencer" can still be effective when very small is that the water droplets can be used to absorb / redirect sound much like the baffling material in a car mufler.
The more expensive mufflers that corsa makes and some others can be very effective in reducing sound without creating any backpressure, but are pretty pricey.
On different boats, I've tried the cheaper fiberglass mufflers (dappers?) as well as the emi with the center slug in it - both made a very large difference in sound.
edit: in the clip below in my signature, the first short sound clip is with emi short clamp ins, center slug in, the second little bit is with the center slugs knocked out - lots sharper, almost like straigh pipes as are the segments running down the river. and in the link just below this paragraph, is an earlier clip with cheap fiberglass mufflers. Note that these were all behind a high compression engine with imco powerflow performance maqnifols (a good bit louder than factory manifolds). You can hear the difference for yourself for between the three. the fiberglass mufflers didn't lose but a couple hundred rpms on a 425+ hp 383... the emi's with the slug in about 400, the emi's with no center slug, no loss relativel to straigh pipe.
http://www.youtube.com/watch?v=33aWuP1K6o8&feature=related
Hope this is helpful.
