Generator Exhaust

[TomT13]

Has anyone re-routed their generator exhaust through the main engine exhaust? My generator currently exhausts out the port side through hull. It leaves black soot, not bad but it's there, on the side of the boat. Big PIA to clean all the time. I have seen other boats where it is exhausted out the main engine exhaust. I have to clean there anyway and figured I could connect or fabricate a T/Y to the exhaust tube inside the boat. Any info would be appreciated.

 

[labrador]

Yes the PO of my boat rerouted them to the transom exhausts for exactly that reason plus to reduce the noise of the cooling water. Also rerouted A/C water to aft tubes to reduce the same as above. Works great however I'm glad he did it as I'm sure it was costly, no idea how much

 

[34Hatt]

I did it on my 34'C have it in the top off the exhaust tube right before the transom has worked out great!
Problem with side exhaust is also when you raft up to others

 

[GJH]

Have you determined why your generator is producing enough soot to cause this problem?

 

[TomT13]

The generator is vintage 1985 Onan so I would expect some amount of soot. The mechanic says its normal. It is exaggerated when we raft up and my exhaust blows out on another boat. Even though it is a "normal" it is just a pain to reach and clean. My 1985 Cat 3208's develop soot as well around the exhaust.

 

[Boatsb]

My 1972 vintage onan does not soot the transom. Maybe there is more than 1 issue.

 

[Trojan]

My 1973 Onan 7.5 side exhaust generator produces no soot. I don't understand how you would have soot on the side of your boat with a water cooled exhaust. I have almost a steady stream of water coming out my exhaust. You also must be careful that you don't create a large amount of back pressure dumping into your main exhaust. My main exhaust tubes are under water when the boat is at rest. That would easily produce to much back pressure. Soot, sounds like you may have something else going on that needs checking.

BILL

 

[Fanfare]

I have had three 12 kw Onans and now a 12.5 kw Phasor generator. All have left some soot on the side of my boat, a little when new, more as they aged. Not a big plume, but visable as grey. I don't recall any difference in this whether buying diesel in the USA, Canada or the Bahamas. After a 200 nmi run I also have to scrub the transom from the main engine's soot, even though my engines are well tuned and don't smoke on startup. I think it is just the nature of diesel engines. I ignore it until I get where I am going, or have some reason to spiff up the boat on the way.

 

[Pascal]

we have the same issue with two NL20 (about 8 years old/4 000 hours). just replaced injector pumps and cleaned/checked/replaced injectors. they're running great but after a while there is definitely some soot along the waterline, aft of the exhaust. It probably takes 100hours for teh soot to become visible but it's indeed a pita to clean.

 

[bobk]

Mine is a 12.5 KW Westerbeke circa 2002. No soot on the side.

Bobk

 

[Avenger]

Dumping the generator exhaust into the main engine pipe is frowned on because exhaust pressure from the main can force water into the gen exhaust system when the generator isn't running. Obviously a lot depends on how it's plumbed. YMMV.

Soot.... Generators are like any other engine. They require maintenance, that means tune-ups at regular intervals. Since generators tend to accumulate hours quickly they probably need to be tuned more frequently than they actually are. Checking valve lash, having the injectors adjusted and verifying timing go a long way to making them burn cleanly and efficiently. We've had reports from the techs at the Volvo dealer that after everything was tuned, what transom sooting remained was eliminated with Stanadyne additive. Fuel quality today is abysmal, so an additive with a cetane booster may be necessary. A good additive will help extend the life of your fuel injection system too.

 

[yachtsmanbill]

Bubba wasnt thinking when he ran the exhaust out the side... should be out the back so when you are at anchor the fumes leave the area. Id hate to raft up next a side exhaust and have to keep the boat closed up for the fumage. Soot or no soot!
Even Bubba #2 changed the subs' to the transom. ws

 

[34Hatt]

We've had reports from the techs at the Volvo dealer that after everything was tuned, what transom sooting remained was eliminated with Stanadyne additive. Fuel quality today is abysmal, so an additive with a cetane booster may be necessary. A good additive will help extend the life of your fuel injection system too.

:

That is a change??????????

 

[Fanfare]

My boat came from the factory in 1966 with both a starboard side exhaust and a fully-plumbed aft exhaust which was never connected. A possible reason for this was that the rubber muffler for the aft system was right under the stbd master bed. This may have put too much vibration and sound into the master cabin. It occurs to me also that a failure of the raw water on the generator could cause the rubber exhaust hose to catch fire. If so it would be almost impossible to get to as the hose is beneath head counters, etc. While my current gen exhaust has temperature sensors for cooling water loss I don't believe the older systen did. I know it did not have one on the aft stateroom muffler, which was of the pass-through type rather than water lift. The generator raw water impeller has always been about the most troublesome part on the boat for failures, in part because it runs so much.

Of course, the main engine exhausts follow the same route, and we have not burned up yet. Pretty hard to sleep in the aft master cabin while the engines are running though.

 

[Avenger]

Not quite sure what you're saying. I was just pointing out that after these guys had done injectors and timing and aftercooler service etc. when all the mechanical problems were eliminated there was still a small amount of transom sooting and the additive cured that. Which would seem to indicate poor combustion qualities of the fuel itself.

Fuel quality has been declining since Low Sulfur Diesel was introduced in '94, but has become particularly poor since Ultra-Low was mandated in '07.

 

[REBrueckner]

Try inserting a short piece of rubber or vinyl hose inside the exhaust outlet...a press fit....so the exhaust is an inch or two from the topside.

Similar idea could work at the stern engine exhausts as well.

 

[jim rosenthal]

I have seen a number of new boats where they had the genset exhaust and the AC cooling exhaust come out the transom. They did this with a small-diameter pipe glassed inside the large diameter exhaust, up at the top. This got the noise and soot, if any, outside the boat, but avoided the risk of a wave getting stuffed up the main tube and into the genset exhaust stream. It could, I suppose, get into the small tube, but the risk seems lessened by the little diameter.

I wish someone had done this with my boat. Of course, without a sound enclosure, my generator is loud enough in the boat that it doesn't get run for long periods. It does not make much soot if any, but it does splash a lot on the starboard side of the boat. The AC outlet, which has a rubber damper on it, makes virtually no noise at all.

 

[luckydave215]

My gen exhausts (20kw Onans) are plumbed both out the sides of the hull and through the transom, with valves to select which is in use.
It's just "more stuff" in the ER of course, but it comes in handy sometimes.
I get no hull soot from any of the engines on board.

 

[34Hatt]

Not quite sure what you're saying. I was just pointing out that after these guys had done injectors and timing and aftercooler service etc. when all the mechanical problems were eliminated there was still a small amount of transom sooting and the additive cured that. Which would seem to indicate poor combustion qualities of the fuel itself.

Fuel quality has been declining since Low Sulfur Diesel was introduced in '94, but has become particularly poor since Ultra-Low was mandated in '07.

I could be wrong but thought most of the time you reply that additives are not needed?

And you really didn't believe in them?

 

[Boatsb]

I could be wrong but thought most of the time you reply that additives are not needed?

And you really didn't believe in them?

Dan remember his business is.....


Those bad additives cost him money.