Soot or smoke on stern with Cummins 370 , Alnin 32+2

Riley Hollingsworth · Post by **Riley Hollingsworth** » Sat Aug 09, 2008 8:17 am

I have an Albin 32+2 and recently had it painted. I guess i didn't notice this when it was faded dark blue instead of light gray. Yesterday I went out on a 15 mile cruise with wind behind me, at 2400 rpm, and stern stayed spotless. Coming back in, with a 15 knot headwind, same rpm and speed, when I got back smoke stain was all over the stern. I saw no smoke in the air either time, and have the Walker fuel sep and air sep and both are clean. Should I have had the blower on, or ports open? Or is it an engine issue? I only had the door open. Fuel is fresh and filters are too. No vents were blocked but the stern is filthy. Ideas?

Post by **chiefrcd** » Sat Aug 09, 2008 2:36 pm

I have a 28 with a 6lp Yanmar and I have always had a sooty back end....

I've tried everything from turbo cleaning and injector cleaning to fuel additives and I still have some soot....the best thing that helped was switching to Valve-tec fuel which I can get locally.....but even with that I still get some soot on the corner of the transom.

Riley Hollingsworth · Post by **Riley Hollingsworth** » Sat Aug 09, 2008 7:48 pm

Thank you--I appreciate your taking the time to comment

jcollins · Post by **jcollins** » Sun Aug 10, 2008 9:16 am

Hi Riley,
There was another thread around here last year about this topic. I'll try and find the link. I think it's the nature of the beast. (pardon the pun)
It's a diesel. There will always be a little. Like Chief mentioned, you can try different additives or switch your fuel.

Post by **Russell** » Sun Aug 10, 2008 10:05 am

I think my comments were in that other thread. After I cleaned my prop the problem reduced but I always see some soot on the corner of my white hull after a long day fishing. When the prop was fouled with barnacles I could see the smoke in the exhaust. Apparently when the engine is struggling to maintain the RPM it adds more fuel which does not burn but creates the smoke. Going into the headwind may have produced more smoke than when you were going downwind because of the engine working harder to maintain the speed.

Post by **jleonard** » Mon Aug 11, 2008 2:32 pm

Yes there is always some soot in the exhaust of a diesel. Yes an overloaded diesel will soot more. Even an underloaded diesel will soot the transom and I have found sea and wind conditions have as much to do with it as anything...my ex boat would soot more if I carried the dinghy on the transom...the change in air flow would blow it back on the transom after it got mixed with the salt water.

On another track I was talking to a long time marina employee a few years ago and he revealed that they never waxed the transom of a diesel powered boat..he said the soot reacted with the wax and made the soot harder to clean off than on plain gelcoat or paint. Can't verify that but take it for what it's worth.

Post by **Russell** » Tue Aug 12, 2008 12:29 pm

Leonard you are correct. I found out this year that waxing makes soot buildup worse. I expected the opposite and was careful to wax the area around the exhaust extra well. Using a teflon wax I expected it to shed the smoke but it attracted even more.

Post by **N4QC** » Tue Aug 12, 2008 5:58 pm

Whereas soot is a result of incomplete fuel combustion and air is an essential component of the combustion process, I would recommend a review of the air requirements need to be supplied to the engine compartment for one’s particular situation. Keep in mind variables such as: wind speed; vessel speed; duct size; vent size for both air intake and air exhaust; and engine compartment heat build up due to factors such as the transmission, alternator, etc. Also, ambient outside temperature and heat rise restrictions for equipment and personnel, all contribute to air requirement needs.

An inadequate supply of air was a contributing factor to my soot problem. A review of the calculations for the amount of air need showed that I was deficient. In addition, the setup for the air supply and air exhaust openings were improper and undersized. I ended up adding a 1500 CFM rated air intake blower and a 240 CFM air exhaust blower to the engine compartment air system, and changed the direction of the through hull exhaust vent grill. Made a big difference…

A CO2 detector was added in the cabin as the engine compartment is now slightly pressurized.

The previous discussion from last year:

viewtopic.php?p=6044&highlight=#6044

Hope this helps,

Albin Owners Group

Albin Owners Group

Soot or smoke on stern with Cummins 370 , Alnin 32+2

Soot or smoke on stern with Cummins 370 , Alnin 32+2