Quieting down a generator

[Z-Worthy]

We have a 1997 400DA with the Westerbeke diesel generator. It's not the most obtrusively loud generator on earth, but it's certainly not quiet either. I'm still not sold on where the most noise comes from: the generator itself or the exhaust? Has anyone had any luck knocking down the noise level of their diesel genny? I don't want to waste my time and/or money if there's really no good solution.

 

[Gofirstclass]

Z- I have a 15KW diesel generator on my boat. When I bought the boat the boat yard owner that was reassembling it for me (after it was shipped from Detroit to Portland, OR) suggested I put an exhaust water separator. I didn't know what it was or what it did, but he promised me that if I wasn't happy with the results he would not charge me for any of the parts or labor.

I had it put on and the difference is amazing. It takes all of the water out of the exhaust and expels it beneath the boat through its own thru-hull. The result is there's no exhaust sound at the back of the boat, none of the gurgling sound that normally goes with a generator exhaust. All you hear when you're standing at the stern is a light hum as the exhaust comes out.

The genset itself is enclosed in a sound barrier and that reduces the noise down to where you hardly hear it and it doesn't interfere with conversation. I feel more of the vibration the generator puts out when running than I hear the sound.

 

[carterchapman]

I priced a sound shield kit for my Westerbeke and it was $1800...uninstalled.

 

[Pietro]

:thumbsup: for the exhaust water separator! I fitted one and got amazing result!

 

[fwebster]

Andrew,

In my case....8.0 Westerbeke and a 450DA......the actual exhaust noise is a small part of the racket going on. The Westerbeke diesels are old style mechanical diesels which means you are going to get some fuel knock.....and there is nothing you can do about it. The valves set pretty loose with something like .010" clearance........and there is nothing you can do about that either. The injectors are another story. I had my injectors removed, cleaned and pop tested. One was found to be dirty which affects how the fuel is atomized. The fluid used for testing is also a cleaner and that cleaned up the bad injector so the only cost was for testing....$75. Having properly firing injectors will reduce the fuel knock....in my case, substantially, so removing, cleaning and testing the injectors is probably worth doing.

However, if you want to pay the cost ($1800-$2000 plus labor) and put up with the inconvenience, a sound shield may help. The problem is that the sound shield blocks access to most of the generator and it must be removed to get to the seawater pump and cooling system. That means you probably won't catch a small water leak early enough to head off some expensive damage. Removing the sound shield for routine maintenance is going to increase your maintenance cost since the sound box has to be removed to get to anything/everything.

 

[Southpaw II]

Sometimes when a generator is loud, it's because it needs an impeller change. Over time, less water flows due to wear or a lost vane, and there is less water in the exhaust...and more noise.

Don

 

[jthatcher]

Just experienced that one myself. New impeller fixed it all up.

 

[Z-Worthy]

In my case....8.0 Westerbeke and a 450DA......the actual exhaust noise is a small part of the racket going on. The Westerbeke diesels are old style mechanical diesels which means you are going to get some fuel knock.....and there is nothing you can do about it. The valves set pretty loose with something like .010" clearance........and there is nothing you can do about that either. The injectors are another story. I had my injectors removed, cleaned and pop tested. One was found to be dirty which affects how the fuel is atomized. The fluid used for testing is also a cleaner and that cleaned up the bad injector so the only cost was for testing....$75. Having properly firing injectors will reduce the fuel knock....in my case, substantially, so removing, cleaning and testing the injectors is probably worth doing.

Frank, I think you're right about the mechanical noise. It's just as loud down in the cabin as it is outside, so I didn't think it was exhaust. Who did the testing and cleaning of your injectors? Any good diesel mechanic or someone specialized?

 

[fwebster]

Any local diesel shop or competent mechanic can remove the injectors and send them to a diesel injection/pump specialty rebuilder for checking. The diesel injector/pump shops have clean rooms and very precise equipment for rebuilding diesel handling equipment so it is common for a mechanic to send out the injectors for service.

Westerbekes also have a specified interval for re-torquing the head. If you don't, then a blown head gasket is in your future. It would be a good idea to have the head re-torqued while the mechanic is on the boat. I'm not sure of the service interval on the 7.6 gen, but I do my 8.0 every 500 hours. Labor, freight and the injector service was under $200.......if an injector needs to be taken apart, the cost would be more.

 

[Yzfspike]

I have read (on this site but could not find the thread), some people have used an Onan water lift muffler on the set up you have. I had a 400DB and same issue. Generator was louder than most. Probably for the reasons Frank described. I had all things serviced properly, new impellers, injectors, check valve clearance......etc. Still loud. Did not get around to installing the Onan muffler, but some others said it made a significant difference.

 

[Alex F]

IMO, the most important thing is determine where's the most noise coming from. I had similar puzzle and I narrowed it down to exhaust noise. To fix it I used a simple approach, I talked to my cummins tech and used his suggestion to install upgraded muffler, which is much larger than stock one. They all laugh at the mufflers SR installs. After about $250 and couple of hrs of my labor the sound was cut down by approx good 30%. I was pretty much satisfied with ROI.

I have to say that from my experience, Onan gennies are much quieter than older Westerbekes, for the reasons Frank described. Those that I personally have heard (on older SR models) made me believe that majority of the noise was actually made by the unit, not so much from the exhaust. Unlike on my boat (or just newer models in general), I think that insulation is better as well, which helps big time. When I open ER hatch, the gen sounds loud, but as soon as I close the hatch, most of the noise goes away to very reasonable level. I caught myself thinking one day, when I came back to my boat from another older SR with Westerbeke "wow, my genny is quite and so is the exhaust". And mine doesn't have the sound shield either.

As with anything, we judge by comparison. I bet that my genny would be even more quieter with soundshield, but I totally agree with Frank in regards to the access and lack of monitoring ability. I store tons of stuff in my ER and anytime I go there I have 100% clear view of the genny and can easily spot a small problem. It would never be the same with a soundshield.

However, unlike in my case (or similar models), I would think that installing soundshield on older boats with Westerbeke would help a lot. But, you have to choose to compromise with access, not to mention the expense.

If I was in your situation, I'd try finding similar model with installed soundshield and judge for yourself if the difference is worth the trouble and money.