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Seaward 25 noisy Yanmar: any point in trying to sound insulate it?

Jul 30, 2019
208
Seaward 25 777 Fort St. James
My 2000 S25 has a Yanmar 2GM20F engine with a partial cowling between it and the cabin. I think this is a fairly common arrangement in sailboats this size with inboard engines. Is there any advantage to be gained from trying to upgrade the insulation and /or extend the cowling? I know we should be sailing and not motoring, but this season we have had a lot of windless days and we like to go out anyway, and the Seaward is an economical motor sailer at about a quart of diesel an hour.
 
Jun 8, 2004
2,549
Catalina 320 Dana Point
My 3gm30 has heavy fiberglass covers fore and aft, I recently tried insulating with a foil/butyl layer and then a foam layer on top. Quite honestly, while slightly effective certainly not worth the effort. It's my understanding that to work really well every possible avenue of sound transmission must be blocked. an apparent impossibility on my boat, a friends french built boat has eggcrate foam insulation factory installed. Can't even hear the engine from the helm, the exhaust water noise is all you hear.
 
Nov 6, 2006
9,183
Hunter 34 Mandeville Louisiana
Noise transmission is a tough thing to work with. Calif Ted is right on. Some things to look at and think about that aren’t as obvious are the motor mounts, the exhaust hose/muffler, and the prop log. If a motor mount is collapsed or badly adjusted, it will transmit a boatload of noise. On the Yanmar mounts, the top steel plate should not be any closer than about 3/8” from the bottom plate. Check all 4, fore and aft ends of each mount. Because the Yanmar moves a lot on its mounts, any binding in the exhaust hose between the engine and muffler will make a lot of noise. Prop shaft log ; if the prop shaft is not centered in the log, the movement of the engine can make the prop shaft hit the inside of the log and make a bunch of noise. Good luck!
 
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Jul 30, 2019
208
Seaward 25 777 Fort St. James
Thank you both. Good information. I have certainly been disappointed in the past with my efforts to dampen noise from vehicle engines, mainly in motor homes. I've been surprised by the noise and vibration from the 2 cylinder Yanmar, whether in or out of gear, since my experience with several 3 and 4 cylinder Yanmar industrial engines is that they are very quiet. I don't like to run this engine above 1500 rpm, but that gets me ~5 knots anyway and sips diesel.

I will follow your suggestions Claude and check mounts etc. Somewhere (here?) I have read that a UK company supplies better and cheaper mounts than Yanmar, but I have not been able to find that information again. Almost certainly my mounts are original, so 20 years young, and well overdue to fit on the worthless-old-spare-parts shelf.
 
Apr 22, 2011
717
Hunter 27 Pecan Grove, Oriental, NC

I installed these mounts recently. They were a perfect fit but a bit softer than the original mounts. They were not wrapped in a Yanmar factory package. Shipping by DHL was fast and not too expensive.

I also replaced all of the engine compartment insulation, as the old stuff was crumbling. Made very little difference in the sound though.
 
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Jul 30, 2019
208
Seaward 25 777 Fort St. James
Thank you, those are indeed the mounts I was looking for.


I installed these mounts recently. They were a perfect fit but a bit softer than the original mounts. They were not wrapped in a Yanmar factory package. Shipping by DHL was fast and not too expensive.

I also replaced all of the engine compartment insulation, as the old stuff was crumbling. Made very little difference in the sound though.
 
Jul 30, 2019
208
Seaward 25 777 Fort St. James
In a word....yes.

Greg
He has a lot more room to play with, get access etc. in his O'Day 322. My access is either from the cabin or through the starboard lazarette. But that is interesting, and the insulation he used, Reflexit, certainly seems to do the job without having to pay the extortionate amounts that a lot of the specialist marine insulation seems to demand.
 
Jan 7, 2011
2,770
Oday 322 East Chicago, IN
He has a lot more room to play with, get access etc. in his O'Day 322. My access is either from the cabin or through the starboard lazarette. But that is interesting, and the insulation he used, Reflexit, certainly seems to do the job without having to pay the extortionate amounts that a lot of the specialist marine insulation seems to demand.
I am not familiar with the OPs boat, but it if the engine is not completely enclosed, it will be loud. Even crappy insulation (I put Reflexit over the old black foam that was disintegrated) made a difference.

Greg
 
Jul 30, 2019
208
Seaward 25 777 Fort St. James
Sorry Greg, I did not connect that it was your own video. Mine is a Seaward 25, and the only cowling forms steps down to the cabin, with large gaps either side. Hence my initial question: is there any point? But I might be able to make it quieter in the cockpit using this Reflexit material.
 
Nov 21, 2012
267
Yamaha 33 Port Ludlow, WA
The engine compartment on Tosca is almost entirely insulated with a heavy, 1/4" thick layer of rubber- like acoustic dampener. It works really well. But the aft bulkhead still had the original ineffective eggcrate foam. I looked into adding more... found it at McMaster Carr... and promptly realized I had quite enough, thank you very much.
 
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