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Muffler for Yamaha 25

Dec 17, 2014
Yamha 25 Gig Harbor
I just bought a 1980 Yamaha 25 sailboat the engine, a yanmar ysm8, needs a new exhaust system including a muffler. Both the mixing elbow and muffler are leaking. I found a source the engine parts, but can't locate a muffler that would work in the engine compartment. Most manufactured mufflers are top in and top out. The existing muffler is bottom out. Does anyone have a solution?


Aug 30, 2010
yahama 25 Hong Kong
I have the YSM8 before , at that time I got a local made top in, side out muffler by stainless steel .
Jan 4, 2008
Yamaha Y25 mkII Long Beach, Ca.
Y25 muffler

You'll have to have one fabricated. I too have looked for a bolt on solution with the same results. I thought the muffler I had was a custom fabrication until I saw it in my Parts list.
I began photo documenting my muffler as it is in need of replacement. Fabricating a new muffler replacement is a ways off but I can dig up the photos if needed.
The Yanmar mixing elbow is a common piece used on many engines. The female threads are prone to deterioration ,I've had good luck welding the cast piece to the riser exiting the exhaust manifold greatly extending its life.

Welcome aboard!
Dec 17, 2014
Yamha 25 Gig Harbor
Re: Y25 muffler

Thank you for the information. After investigating ready made mufflers including inline vernalifts ,I had a sheet metal shop cut out the old leaking bottom of the muffler and weld in a new SS 316 bottom. The cost was less than a ready made muffler and less work to reinstall.
Also some where else on this site there's a discussion about the mixing elbow adapter(left/right threads). I discover that to install the extension between the engine and mixing elbow is fairly simply. The extension is 2 inch steel pipe nipple of proper length with a female coupler into which the adapter's right hand is threaded. The other end of the adapter threads into the left hand threads of the mixing elbow. I'm told the preferred pipe is black iron pipe.