Exhaust soot Yanmar 4JH3E

[HarryvdMeer]

Reaching out to anyone who has been able to fix problem of minor soot developing on hull after 50-60 hrs of cruising
Hunter 44DS 2004
Yanmar 4JH3E
2400 hrs (1500 hrs added during last 27 months)
no visible smoke
engine runs very well and starts immediately
WOT rpm 3800
Cruise rpm 2800 (75% of WOT)
No prolonged idling as I use generator and solar for charging housebank
Fuel remains fresh due to cruising
Oil, oil filter and primary and secondary fuel filters changes per manual. Never had water in primary fuel filter
Inside of exhaust elbow clean, no carbon buildup
Other than oil, oil filter, fuel filters and belt, no maintenance has been done since I have owned the boat (Aug 2020).
Possible causes:
- valve clearance
- injection timing
- injectors dirty

Any help is much appreciated.

 

[Ralph Johnstone]

Where is the exhaust discharge on the hull located ? A picture would help.

 

[jssailem]

Possible causes:
- valve clearance
- injection timing
- injectors dirty

Certainly those are possible suspects.

When did you last look at your prop?
I shared this several years ago when I felt my prop was bogging down my engine/boat and I was having to clean oily exhaust soot off the transom. When I advanced the throttle to cruise, the stern would drop a good foot or more putting my exhaust tube at or below the water line.

You can see the dirty oil/soot smudge on the stern of Hadley docked to the left. Gross. Like that commercial of years ago.. "Ring around the collar"

I switched the old school prop,

For a new modern design.

Now I get thrust without the smog.

 

[HarryvdMeer]

See attached pic. I have a max prop which was installed by the previous owner, who mentioned that he believed it was underpitched. WOT would get to 4000 rpm. So about 1 year ago, I changed the pitch 1 number, which yielded slightly lower WOT rpm of 3800. I noticed the soot after that. I do consider putting the original pitch back as the boat is out of the water for a bottom paint job. However, I do not want to mask an other problem.

 

[jssailem]

What are your engine specs for WOT? Have you discussed the issue with Max Prop?
I would suspect that is more the culprit than an issue in the engine. I always try to look back at anything that has changed first. Change of pitch along with appearance of the soot, could identify with the engine bogging while WOT.

Then I look to the simplest fix. It would be easy to check the valves for adjustment.

 

[HarryvdMeer]

Thank you. The valve clearance is going to be checked on Monday.