My 1977 43' Viking motor yacht seems to be way too loud. Detroit 671-N motors. Will new mufflers help? Do mufflers just wear out? What do you look for in new mufflers? I have owned the boat 17 years and just started to bother me. Probably bothered dockmates for years.
mufflers
- Thread starter woodchuck
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BillyIII....not wanting to hijack the thread, but I'm wondering about your comment on low raw water circulation contributing to loud mufflers. I suppose that's because water itself, when flowing through mufflers, dampens some noise? I know the answer might be a "duh," but I figured I'd ask anyway.
Thanks for your thoughts.
V/R
Thanks for your thoughts.
V/R
William yes by design the water helps act as a sound absorber in the boat's muffler system.
I would look at the water being expelled and keep my eye's on the temperature gauge. A loud boat can be an early warning that something is resitricting the raw water flow. All bets are off if it's a dry stack exhaust.
Bill
I would look at the water being expelled and keep my eye's on the temperature gauge. A loud boat can be an early warning that something is resitricting the raw water flow. All bets are off if it's a dry stack exhaust.
Bill
Woodchuck, the same boat as yours idled by me last week and I noticed how loud the exhaust was. I could tell it had 671's because I have them too. I think that was how they were built. Probably nothing wrong.
I believe keeping back pressure low is important for these motors. You also have the issue of access and room for larger mufflers since they may be below your aft cabin floor. Probably worth some professional estimates on parts. The exhaust size should stay the same so install could be DIY.
I believe keeping back pressure low is important for these motors. You also have the issue of access and room for larger mufflers since they may be below your aft cabin floor. Probably worth some professional estimates on parts. The exhaust size should stay the same so install could be DIY.
it is possible that you have broken a baffle loose in one of the mufflers and the difference is noticeable. I think Bill is spot on with checking the water flow first. use a bucket and stop watch on each side if its not clear.
as others have noted, back pressure or lack thereof, is very important and I wouldn't purchase any muffler without some professional help on the engineering side. any reputable custom muffler mfg can design a system or sell you one from production that suits your purpose. you will need to identify the specific design back pressure your engine requires. you can get this from Detroit if its not called out in your engine manuals.
as others have noted, back pressure or lack thereof, is very important and I wouldn't purchase any muffler without some professional help on the engineering side. any reputable custom muffler mfg can design a system or sell you one from production that suits your purpose. you will need to identify the specific design back pressure your engine requires. you can get this from Detroit if its not called out in your engine manuals.
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We have had several smaller boats that were kept on a lift - to Billy's point - when I first crank up our boat it is loud for 5-10 seconds until water starts flowing out of the exhaust. In my case it is because everthing on the aft side of the risers drains while the boat is on the lift. Bottom line, whatflow thrugh the exhuast definitely impacts how loud it is.
I don't know enough about 6-71's and your model Viking's exhaust. It's possible the restriction might be in the muffler but it's also possible that the that the restricted flow could be something else as in engine related. I would have someone with knowledge of your vessel to check it out before it becomes a potential issue.
Then again I could be wrong but it seems like it should be checked out.
Bill
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One of the ships I worked on back in the early 80's had 671's for ship service generators. The engineers always referred to them as 'Screaming Detroits'! They were eventually replaced with Cat 3208's. I know not relevant just thought I'd toss that in there! ;-)
2 stroke diesels need to breath, they have blowers that push air thru the cylinders, it's called scavenging. Low back pressure is important. Some of us might remember the old greyhound and city buses, they where loud and stinky.