3880/3860/4080/4060/3780 Generator Exhaust Mod

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3880/3860/4080/4060/3780 Generator Exhaust Mod

Postby rommer » Tue Nov 20, 2007 7:50 pm

This mod dramatically quiets the generator exhaust noise.

Image

Image

The exhaust extension is a pressure fit, however there is a stainless steel clamp holding the entire assembly in place to the swim platform support so it doesn't move.

The rubber piece is available at your local Home Depot/Lowes and is a wet vac adaptor for going from a large hose to smaller hose. RIDGID Universal Power Tool Adaptor Model VT1407

Image
(Available at http://www.ridgidparts.com/accessories/VT1407.phtml)

Cut at the first step to the right from the square part. Use a dremmel type tool to reduce or taper the edge to help it fit in and the press in. The largest diameter fits perfectly around a 2" PVC fitting.

Total cost about $20

Cuts the noise which is amplified by the large swim platform WAY down!
Wake-N-Waves
2004 Silverton 48/50C
2003 Regal 3880 (Traded in and sold)
2003 Regal 2860 (Sold)
West Milford, NJ
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Re: 3880 Generator Exhaust Mod

Postby Southern Cross » Sun Dec 09, 2007 2:13 pm

Rommer,

I remember you mentioned on the original post that you drilled a small hole in the PVC to break the siphon risk. Probably worth mentioning.
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Re: 3880 Generator Exhaust Mod

Postby rommer » Sun Dec 09, 2007 7:07 pm

Good point Martin, thanks!

(I did run for over a year in the water before putting the hole in this past summer. No problems but I do sleep better knowing there is a small siphon break.)
Wake-N-Waves
2004 Silverton 48/50C
2003 Regal 3880 (Traded in and sold)
2003 Regal 2860 (Sold)
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Re: 3880 Generator Exhaust Mod

Postby nawtical1 » Tue Dec 18, 2007 8:34 am

Thanks for reposting. This is on my winter project list.
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Re: 3880 Generator Exhaust Mod

Postby rommer » Wed Jul 30, 2008 6:17 am

Has anyone used this mod on a gasoline powered 3860/3880/4060/4080?
Wake-N-Waves
2004 Silverton 48/50C
2003 Regal 3880 (Traded in and sold)
2003 Regal 2860 (Sold)
West Milford, NJ
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Re: 3880 Generator Exhaust Mod

Postby kellyg » Wed Jul 30, 2008 9:58 am

John,

I did the modification last year and it did quiet the exhaust quite a bit.
Gary Kelly
Mount Sinai, NY
2001 Regal 3780
REPOWERED WITH YANMAR 2011
Smooth seas never made a skillful mariner
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Re: 3880 Generator Exhaust Mod

Postby rommer » Wed Jul 30, 2008 10:04 am

Gary

Can i assume that you have not had any issues with the gas generator since doing the install?

The reason I ask is a friend at the marina recently purchased a 4060 with gas and the generator noise is fairly loud. I'd like to get him to try the mod but wanted to make sure other gas users have had no problems with the modification. I
Wake-N-Waves
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2003 Regal 3880 (Traded in and sold)
2003 Regal 2860 (Sold)
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Re: 3880 Generator Exhaust Mod

Postby Chris_in_Texas » Wed Jul 30, 2008 10:11 am

To bad my generator exhaust is out the starboard side of the boat. I would like to mute it a bit more.

I guess I need to get 10'itis. :)
Thanks, Chris
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Re: 3880 Generator Exhaust Mod

Postby PJS » Wed Jul 30, 2008 11:24 am

I also added the rommer modification to the genny (Kohler gas) exhaust on my 2003 3860. It does make a significant reduction in noise.
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Re: 3880 Generator Exhaust Mod

Postby kellyg » Mon Aug 04, 2008 12:33 pm

John,

I did not place the discharge underwater as you did under the advice of my Westerbeke tech.
It is about 4 inches above the water line, but I did drill a hole for vacuum break just in case. The noise was diminshed around 30%, but later this season I will reroute the entire exhaust as to have a port discharge.
Gary Kelly
Mount Sinai, NY
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Re: 3880 Generator Exhaust Mod

Postby elvis » Thu Aug 14, 2008 11:20 am

I would be concerned about back-pressure on the exhaust. The generator is not designed to push exhaust and cooling water through a few inches of seawater, so it will likely run less efficiently and a bit hotter. The extra exhaust pressure could cause additional exhaust gasses to leak into the boat if there's a leak in the exhaust hose, so keep an eye on that as well. It will also put a bit of extra load on the impeller. I think the anti-siphon hole may help a bit, as it will allow some pressure to escape, but not much if the exhaust is that much quieter.

I have seen at least one manufacturer move their engine exhaust ports underwater, but there is a second port above the waterline for running at idle to reduce back pressure.
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Re: 3880 Generator Exhaust Mod

Postby rommer » Thu Aug 14, 2008 2:17 pm

With properly designed exhaust systems the added back pressure here is very minimal.
Wake-N-Waves
2004 Silverton 48/50C
2003 Regal 3880 (Traded in and sold)
2003 Regal 2860 (Sold)
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Re: 3880 Generator Exhaust Mod

Postby Canada » Mon Aug 18, 2008 2:53 pm

Just want to thank you Captain. Rudy's World (3860) just installed your modification. Works great and now we don't have to cringe or start yelling every time he starts his geni. I would say it cut down the noise by 80% and is now in line with the rest of us. ie: you can hear a gentle purring / bubbling type of thing but it is definitley not a roar as in the past. Brian on Lock Knut is next.

Thanks again.
Greg & Kathy
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Re: 3880 Generator Exhaust Mod

Postby rommer » Mon Aug 18, 2008 2:57 pm

Thanks for the update Greg!

Our friends recently purchased a 4060 with gas and I need all the feedback I can get to convince him to do the mod. He doesn't like doing "computer" so I'll have to print this thread out for him ;)
Wake-N-Waves
2004 Silverton 48/50C
2003 Regal 3880 (Traded in and sold)
2003 Regal 2860 (Sold)
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Re: 3880 Generator Exhaust Mod

Postby rommer » Mon Aug 18, 2008 3:02 pm

elvis wrote:
I have seen at least one manufacturer move their engine exhaust ports underwater, but there is a second port above the waterline for running at idle to reduce back pressure.



But generators don't idle. They may run at no load but most run at a fixed RPM speed of either 1800 or 3600 in the 60hz world or 1500/3000 in the 50hz world.

The new Honda type inverter/generators are an exception in that they do change speed based on load but they are not water cooled anyway.
Wake-N-Waves
2004 Silverton 48/50C
2003 Regal 3880 (Traded in and sold)
2003 Regal 2860 (Sold)
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Re: 3880 Generator Exhaust Mod

Postby Chris_in_Texas » Mon Aug 18, 2008 9:04 pm

Hey Rommer,

Does the 3880 use the 7.3KW Kohler? Does it already use a silencer? If its the 7.3 then your allowed a 1.42PSI exhaust backpressure limit. You can also put a slight lift between the silencer and the exhaust outlet to quite it down some more and prevent water backwash into the silencer.

If the PVC tube only runs a few inches into the water, I don't think you could approach the 1.42PSI limit, although you would have to find out the date on the silencer to see what the normal drop is there.

For good reference material on the Kohlers you can go to:

http://www.marinegenerators.info/kohler/
Thanks, Chris
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Re: 3880 Generator Exhaust Mod

Postby rommer » Tue Aug 19, 2008 6:33 am

Nope, I have the 8KW diesel Kohler. It uses a water lift muffler to reduce exhaust noise.

The big problem with Regals approach on some boats is that the swim platform becomes a huge sounding board which amplifies the noise. The solution used by many of us seems to solve that problem with no ill effects to the equipment.

FWIW - when the boat is running the exhaust mod is out of the water so back pressure is moot under running conditions.
Wake-N-Waves
2004 Silverton 48/50C
2003 Regal 3880 (Traded in and sold)
2003 Regal 2860 (Sold)
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Re: 3880/3860/4080/4060/3780 Generator Exhaust Mod

Postby Jim_In_Calif » Tue May 05, 2009 1:48 pm

Hello All

I was wondering how many inches does the pipe go in to the water?

Also how large of a hole needs to be drilled in to the pipe for anti siphon. (what's a small hole).

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Re: 3880/3860/4080/4060/3780 Generator Exhaust Mod

Postby PJS » Wed May 06, 2009 10:57 am

My installation has the pvc running 5-6" below the surface when the boat is at rest. I don't remember the exact size relief hole I drilled but it was less than 1/4". Also, this year I put some bottom paint on the pvc as it was covered with zebra mussels at haul out last season. That's the first time I've had any trouble with the zebra mussels but I guess they are all over the great lakes.
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Re: 3880/3860/4080/4060/3780 Generator Exhaust Mod

Postby Jim_In_Calif » Thu May 14, 2009 12:28 pm

Hello all

Has anyone made this mod on a westerbeke gen set (8 KW) I have a 3780 and was wondering if any one has done this on the westerbeke.

Is ther any difference on the Westerbeke?

Cheers Jim
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