Yanmar exhaust smut

[Adaero]

Just reading the post about oil change intervals reminded me to ask about exhaust smut. When we have to motor for more than a couple of hours we find the side of the boat around the exhaust is covered in black smut. Its a pig to get off so I was wondering if there is anything we can do engine wise to try and stop it?
The engines are 4JH4 Yanmars and only have around 250 hours each and they have recently had an oil change which improved it slightly but its still there. Someone in the marina mentioned an oil addative and also a diesel one but I'm reluctant to start putting addatives in on such new engines.
Any advice would be appreciated.

 

[Marsupial]

To an extent the yanmar is a bit prone to that but have someone do some calculations on the prop size vs power output and try and determine if the props are right for the engines. If yes they are OK then It could also be that the engines are still a bit tight (new and not run in) and are not giving their full power.

 

[pampas]

Try exstending the outlet about 6" with a clear plastic tube. Very effective with sugar scoop transoms,did my mates and it no longer occurrs.

ps. cut the tube at about 60 degree angle at the rear end to stop drips .

 

[Cloven]

Agree with pampas - that's the way to go.

 

[Scotty_Tradewind]

If you ran them in without working them too hard perhaps the injectors could do with a birthday. Injector cleaning additive slipped into the primary filter for a short blast, when the engine is hot may be an idea.
Some diesels need to be working hard to not produce soot but also may produce soot when forced.
Many really hate idling for long periods so it may be trial and error with the throttle for a while. If you have a long slow run to and from your mooring it may be the problem.
Best of luck, and try not to roll us yachties about too much /forums/images/graemlins/wink.gif