generator exhaust into main exhaust

[tunasdream]

I'm placing my new generator below deck and want to route it threw the main exhaust system. I've seen plenty of sport fish style boats do this is there something special that needs to be done. My plan would be to have the generator go into a water lift muffler then the gooseneck dump into the top side of the main exhaust on a t or y. I cant think of any obvious issues with this but figured id ask the question to see if there was something I'm missing. Thanks in advanced.

 

[easyskankin441]

While this is an option. you still have to run the gen. exhaust to the stern to be compliant. Most likely easier to just install a separate exhaust in my opinion.

 

[tunasdream]

Is there a specific reason as to why they run a shroud over the exhaust? is it so stop a scavenging effect from the exhaust?

 

[tunasdream]

Thinking more about this now, I'm thinking what I'm missing is the back pressure and the exhaust finding its way back to the cab or threw the main engine if not routed all the way to the stern.

 

[captjohn]

If both the main engine and the generator used water lift mufflers, I suspect it's not a problem. But I get an uneasy feeling about doing this if they're not, and the possibility of learning the hard way at the expense of your main engine. If possible, I'd ask a boat builder or an engine manufacturer that has done this before if there are any potential "pitfalls" here.

 

[Firened]

Hi
I have that setup. 38 Blackfin 6 v -92. Gen exhaust goes to water lift muffler then exhaust hose to side of 8 in exhaust pipe. It exits inside pipe but at the very end. Shoots out straight into water. I can get pictures if you want to see it.

 

[tunasdream]

it seems the general consensus is that the merge would have to be right at the end of the exhaust or just to run its own exhaust which will probably be how I do it.

 

[kehoff]

I went to look at my Wilbur and it is run separately , side by side , I actually thought it was dumped into the main exh pipe ,anyway that is how mine is run , not sure of the reason

 

[enginecom]

Remember this. Never use a scoop strainer on the raw water intake. When underway those will force water into the generator when its not running. The exhaust mixing elbow can fill a water lift and send that water into the generator engine. Seen this happen with new installations with disastrous results. I prefer a separate generator exhaust outlet. If the mixing elbow is under 12" above the waterline add a siphon break aka vented loop before the raw water hose that feeds the elbow. The exhaust outlet should be going down hill about 3 degrees and check valves in the exhaust help. There are more problems with generators when they are off.

 

[Jay Michaud]

Hi Tunasdream,,
First, for full disclosure here, I'm an Accredited Marine Surveyor SAMS/AMS). I survey vessels to determine their condition & value for many reasons, including insurance coverage.

Now that that's on the table, if I were to survey your vessel for any reason, including re-insurance, I confess I would be compelled to report the merged exhaust system, as you have described it, to be out of compliance with ABYC (American Boat & Yacht Council) P-1 INSTALLATION OF EXHAUST SYSTEMS FOR PROPULSION AND AUXILIARY ENGINES, specifically the following requirements:

1.5.5 A separate exhaust system shall be provided for each engine installation
1.5.2 TIle exhaust system shall be designed so that the back pressure does not exceed that specified by the engine manufacturer.
I S II Exhaust systems shall be designed so that reverse operation cannot force water into the exhaust manifold of a non-operating auxiliary engine such as a generator.
L5JO No additional discharges other than cooling water may share the exhaust gas passage,

It would be in your best interest to provide an independent generator exhaust system from the git-go, rather than having to re-engineer the system to compliance standards and replace the non-compliant system. Your insurance carrier will require complete compliance before issuing a policy.

Captain Jay Michaud, SAMS, AMS
25 Ocean Avenue
Marblehead, Massachusetts 01945
781.639.0001
www.MarineSurveys.com

 

[captjohn]

Remember this. Never use a scoop strainer on the raw water intake. When underway those will force water into the generator when its not running. The exhaust mixing elbow can fill a water lift and send that water into the generator engine. Seen this happen with new installations with disastrous results. I prefer a separate generator exhaust outlet. If the mixing elbow is under 12" above the waterline add a siphon break aka vented loop before the raw water hose that feeds the elbow. The exhaust outlet should be going down hill about 3 degrees and check valves in the exhaust help. There are more problems with generators when they are off.

Absolutely true!!! And most toilets as well!

 

[Genius]

ABYC police are watching you

 

[[email protected]]

I have the Cummins installation instructions and they don't allow any mixing of any engine's exhaust under any conditions, and an installation review would fail if the exhausts were tied together, even a genset separate tube all the way to the transom. That separate tube inside the main exhaust would work fine but the factory doesn't want any grey area's.

 

[Jay Michaud]

ABYC police are watching you

Cute comment, I got a chuckle out of it!

Seriously though, Tunasdream should be commended for asking for advice before embarking on a complex and perhaps costly endeavor.

All marine surveyors must inspect to the current standards, including, but not limited to:
1. A recognized (SAMS, NAMS) Code of Ethics and Rules of Practice
2. American Boat and Yacht Council (ABYC) Standards and Recommendations
3. Title 46 United States Code (USC) Title 33 and 46 of the Code of Federal Regulations (CFR)
4. National Fire Protection Association (NFPA) Standards and Recommendations
For the most part, the Standards & Recommendations were born from the consequences and results of events and/or accidents caused by un-wise & perhaps dangerous practices. Kinda like not listening to your mother's warning not to touch the hot stove, but you do it anyway, and once you've been bunt, you get the picture. You will never attempt that again.

Although I found your comment humorous, Safety at Sea is not a laughing matter. Over the past twenty-some-odd-years, I've inspected (surveyed) many vessels which have undergone myriads of DIY refits & projects. Many of those refits rival work done by professionals, however some have not.

I'm not the ABYC "Police", nor are any of my peers. We must, however report what we find. Should an observation be out of compliance, we are bound to report the finding(s) to the best of our ability. That being the case, anyone attempting to start a major project, like that of Tunasdream, are very wise to seek out competent advise before attempting the changes to the vessel's systems.

Again, I commend Tunasdream for asking the proper questions before getting ars-deep in the refit.

Captain Jay Michaud, SAMS, AMS
25 Ocean Avenue
Marblehead, Massachusetts 01945
781.639.0001
www.MarineSurveys.com

 

[ccc]

Thinking more about this now, I'm thinking what I'm missing is the back pressure and the exhaust finding its way back to the cab or threw the main engine if not routed all the way to the stern.

Bingo. Gases from one engine backing up into the other can cause all sorts of corrosion and other issues, not least of which can (and has proven to) be leakage into the vessel’s interior spaces via the non-running engine. CO poisoning and death have resulted.