Generator exhaust sooting the hull

[Nick F]

Does anyone else suffer this problem? As the generator exhaust sputters out from the side of the hull it builds up a layer of sooty deposits all along that side of the boat. I have a Northern Lights M643 (5 kVA) with 1700 hours on it. 1500h when I bought the boat 3 years ago.

What are your thoughts? New injectors?

 

[MVPacific]

Assuming you’ve already confirmed clean fuel and air filters, and correct valve timing…..ULSD dramatically reduced the amount of soot emitted from diesels. That said, unless a diesel engine is run hard enough to get EGT to 800 deg F, its exhaust still contains unburned fuel and carbon, which can slowly discolor whatever is nearby. Your best bet is to run that engine at 75% of rated output for as much of each charging session as you can. I understand that it’s impossible to do on many boats.

 

[kapnd]

Does anyone else suffer this problem? As the generator exhaust sputters out from the side of the hull it builds up a layer of sooty deposits all along that side of the boat. I have a Northern Lights M643 (5 kVA) with 1700 hours on it. 1500h when I bought the boat 3 years ago.

What are your thoughts? New injectors?

It’s probably running under loaded, passing unburned fuel, as noted by MVPacific above.
Ever wonder why some commercial boats burn those big halogen lights 24/7?

 

[O C Diver]

The exhaust was originally on the side of my boat. Moving it to the transom under the swim platform made a big difference. If moving it isn't in your plans, clean the hull thoroughly and wax it. It's much easier to clean soot off wax.

Ted

 

[Nick F]

The exhaust was originally on the side of my boat. Moving it to the transom under the swim platform made a big difference. If moving it isn't in your plans, clean the hull thoroughly and wax it. It's much easier to clean soot off wax.

Ted

Thanks Ted. When you said it made a difference did you mean that you also had sooting problems? I would like to know if this is a general problem.

I am also toying with the idea of moving the exhaust to the transom - probably together with a water/gas separator.

 

[O C Diver]

Thanks Ted. When you said it made a difference did you mean that you also had sooting problems? I would like to know if this is a general problem.

I am also toying with the idea of moving the exhaust to the transom - probably together with a water/gas separator.

My exhausts (engine and generator) were combined and existed on the starboard side. Both engines had lift mufflers. The generator had a water gas separator which also reduced the sound and dumped the water through the hull.

If your generator doesn't have a lift muffler, I would add that first. More of the carbon gets trapped in the water.

When I moved the the exhausts to the transom, I used the 8" exhaust tube from the original engine. The bottom of the tube was in the water, so no splash at anchor. I glassed in the water drain from the separator and ran both tubes into the exhaust. As a result of the larger tube no spray and the separator captured more of the carbon in the water. It's also a very quiet exhaust.

Ted

 

[Sababa]

I had this problem with the same generator and after replacing the injectors and adjusting the timing and valve clearances to no effect it turned out to be poor air flow in to the sound shield. Try running it with the inspection port open and see if that solves the problem.

 

[Nick F]

I had this problem with the same generator and after replacing the injectors and adjusting the timing and valve clearances to no effect it turned out to be poor air flow in to the sound shield. Try running it with the inspection port open and see if that solves the problem.

Thanks Sababa, but I removed the sound shield two years ago for better access.

 

[Nick F]

If your generator doesn't have a lift muffler, I would add that first. More of the carbon gets trapped in the water.

I forgot to mention - I have a water lift muffler in the exhaust.

 

[O C Diver]

I forgot to mention - I have a water lift muffler in the exhaust.

One of the questions I would want to answer before making changes is whether the carbon build up is from the exhaust gas or water. If you're generating fog or spray around the entire inside of the outlet, versus water falling away from the hull, the fog / spray carbon residue may be the culprit instead of the exhaust gas.

With my boat, there is no fog, only water out the exhaust tube. Also, with the exhaust out the transom, you can allow the tube to stick out some number of inches, especially if there's a swim platform to protect it. Mine is likely around 3 or 4 inches.

Ted

 

[t/t CVN69]

Put new generators on a boat many years ago with first trip after sea trials from Chesapeake Bay to Bermuda. Not warm enough for air con and not cool enough for heat so the only way we could load the generators enough for breakin was to run all 3 refrig systems and the watermaker along with all the lights on to load the battery charger. Killed cruising sailor friends on board that we were dumping 25gph of sweet water over the side! Oh-and no soot....

 

[bykpjfk]

Does anyone else suffer this problem? As the generator exhaust sputters out from the side of the hull it builds up a layer of sooty deposits all along that side of the boat. I have a Northern Lights M643 (5 kVA) with 1700 hours on it. 1500h when I bought the boat 3 years ago.

What are your thoughts? New injectors?

I would load my fuel tank with Diesel Klean and see. Pretty cheap stuff. Raises the cetane a bit, which some diesels require. My Yanmar's sooted the transom bad until I tried this stuff. US diesel has the lowest cetane rating in the world (40). Many foreign diesels require 44.

 

[Lepke]

If the soot is new, injectors can get buildups on the tips that disrupt the spray pattern. This causes bigger droplets that don't fully combust and leads to soot and fuel sheen. Tips can be cleaned manually or with chemical additives like [B]bykpjfk[/B] recommends. Or tips can be replaced. All my fuel is treated with a conditioner that raises the cetane rating along with other benefits. I have no generator soot problems with my two generators that side exhaust via a water muffler. Both engines are old. 1972 Perkins and 1986 Onan.
When I do run a generator, I load it up. Doing laundry, heating water, making water, and if necessary I put a couple electric heaters on deck to keep my load at 50% or better. It burns cleaner and keeps the cylinder walls from glazing.
Raising the cetane rating also gives better mileage.

 

[JimKane]

Does anyone else suffer this problem? As the generator exhaust sputters out from the side of the hull it builds up a layer of sooty deposits all along that side of the boat. I have a Northern Lights M643 (5 kVA) with 1700 hours on it. 1500h when I bought the boat 3 years ago.

What are your thoughts? New injectors?

The solution is simple. Remove the high pressure pump and nozzles. Take them to a diesel repair shop for testing and rebuild. Reinstall and your problem will be resolved.

 

[Comodave]

You can also wax around the exhaust on the hull with Rejex wax. It may help to get the soot off easier.

 

[Barking Sands]

I rebuilt my gen nozzles myself. They were, I believe, old Bosch style as I think yours may be. They are super simple and if you can research the appropriate tractor equivalent P/Ns parts and even injector assys are much much less.
I bought one of these to flow check the nozzle before doing anything since I figured flow checking my own nozzles may come in handy. It works well. Mine flow checked terribly with fuel dribbling out under just a few hundred PSI and a very poor spray pattern.

Amazon.com

I may be off track, but a quick look and search seems to imply the NL M643 is a Shibaura base engine. If you can confirm tractor equivalent then buying nozzles or injectors new and swapping out can be a cheaper alternative. And you then have spares after you flow check the removed ones. I personally would do the nozzles or injectors first since its easy and can be done cheaply and has a high probability of improvement.

https://www.fridayparts.com/fuel-injector-325-70939-32570939-for-shibaura?gad_source=1&gad_campaignid=21838817472&gbraid=0AAAAApaBdCX06msbPn2EkIwjHg4s5xIP8&gclid=Cj0KCQjwhafEBhCcARIsAEGZEKIctmO_BawyhxGzUzSBCUZehKMds8fH-TIxG4BJokjLhDyWccPRzKkaAsIoEALw_wcB

If you can further research just the nozzle tip you can usually get them for about $25 for a pack of 6. And cleaning, swapping nozzle tip and flow checking is quite easy.

I had quite a bit of soot and black smoke under heavy loads. Changing nozzle tips and an oil change reduced the smoke probably 90% and it runs much smoother (Westerbeke 4.4KW/Mitsubishi K2C)

 

[Barking Sands]

I forgot...I actually video'd my nozzle refurbish..lol.

 

[firehoser75]

Some good advice so far. I suggest a cetane/diesel cleaner fuel additive (Startron for example), and ensuring that you put the gen set under at least 50% (better 75%) load each time you run it. As Lepke said, put some portable electric space heaters on deck if needed to add load. However, passing boaters will wonder why you are trying to heat the outdoors. Waxing the area to make cleaning easier is also a good idea.
If these don't work to your satisfaction, then explore the more serious measures also discussed above (like changing the exhaust, injector rebuild, etc.)