Exhaust soot on transom

[Freedom]

While making the trip to Catalina this weekend I experienced excessive exhaust soot on the transom and noticeable exhaust odor in the cockpit. Boat is a 93 Catalina 34 mk 1.5 with the M35 Universal engine. I just changed oil, fuel filters, trans fluid etc. engine ran great at 2200rpms for the 12 hour passage from San Diego. Any suggestions or is this normal during long motor passages. Engine only has 600 hours on it and has been well taken care of.

[lazybone]

Could be valve timing or fouled injectors?

(assuming the rpm is correct and is what you normally cruise at.)

[Clay Greene]

Did you have wind behind you and/or a following sea?  That always produced more soot on the transom, some of which we got in any conditions.  Unless the engine was running rough or you noticed a persistent black or white color in the exhaust, I don't think it is anything to worry about. 

[Ken Juul]

Google says that is about a 70 mile trip.  10-12 hours if you are just motoring.  Is this the first time you made this long of a trip?  If yes,  store the info away to compare to your next long trip.  If no, is the exhaust build up worse than the last one?  It was probably more than a weekend, maybe with some extra friends.. was the boat heavier than normal which would cause the engine to work harder.

My guess is you don't have a problem.  Boats get dirty with use.  Spend some time cleaning and rewaxing.  Then do it all over again :)

[Ron Hill]

Free : If you weren't pushing it, all that is happening is your 21 year old engine is starting to show its' age.

[Freedom]

Thanks for the input everyone, I'll break out the buffer next week and get it all cleaned up and keep an eye on it. Ken, yes it was a 12 hour trip head to wind, swell and current so she was working a little more than normal. Probable not a bad thing to get the cob webs blown out of the engine. Usually I only use the motor to get in and out of the marina, so running the motor for that long is a bit out of the ordinary. I'm gonna top off the fuel next week and put some Lucas treatment in her to keep those valves and pistons well lubed and maybe well head out to Catalina again in a few months. Im also going to change out the air filter element. Anyone heard of putting a K&N cone filter on to replace the original filter can?

[Ken Juul]

K&Ns work well, but are expensive.  I replace my foam filter about every two years.  Go to a fabric store, they usually have foam by the roll in either 24 or 36 inch widths.  Buy a foot, you have enough for two or three replacements.  Cut to size and sew/glue the ends together.

[sail4dale]

Are you sure your actual engine speed was 2200 RPM?  My meter has always reads low by a 25% factor.  (checked out with  a manual tach)

On True Luff if I read 2200 my actual engine speed would be 2750 and with my 3 blade 10 pitch folding prop
I would be slightly overloading and getting a bit of smoke.  I usually cruise at actual engine speed
of 2400 (reading ablut 1900) and get 7 plus knots without smokeing.  However ..... over a period of cruising there appears some black smudging around the exhaust.

No I have not heard of that cone filter .... why replace it.  My Racor and spin-on has served me well.

[Paulus]

I put a K&N filter.  This is my second summer with it.  I seem to have more soot but that could be to my transmission problem.  When the mechanic looked at my transmission he also noted the soot on the transom.  Wondered if the new filter was getting enough air and also that I needed to clean it.  I did clean it mid way through the summer with the cleaning kit that came with it but it never cleaned back to the original red as the instructions said it would.  Going to clean it this fall and if it does not clean to the original red, I am going to try to return it to NAPA as it has a life time warranty on it.  May go back to the original filter??
Paul

[Les Luzar]

Free,
It is a good idea to run your engine at cruising temperature every time you take her out. Diesel engines like to be run, and you need to burn off the internal condensation and burn your fuel cleaner. I always run my engine at least twenty minutes at cruising speed every time I go out. I make it a point to do this. In Long Beach for me that means running hard out the jetty and then out to the breakwall (about 2 miles). This is good for the engine, and it helps me use up my fuel. Even being diligent about this, I still only use about 15 gallons a year. I sail almost every weekend, and I still have a hard time using up the fuel in the tank. You don't want old fuel, and you don't want condensation in your fuel tank. So I try hard to use up the fuel in the tank so that I can keep replenishing it. Just a thought....

A few years ago I repitched my prop from 9" to 10

[Les Luzar]

As I was saying, ever since I repitched my prop from 9" to 10" I noticed the difference on the engine load, and at 2500 RPM I now have some white smoke (steam?) coming out my exhaust. With the increased pitch, the engine seems to run a bit hotter as well, but well within the safety range. This winter I am going to remove my HX for a service and see if this affects this situation. Also, I am experimenting with slightly slower RPM 2300, 2400 at cruising speed to see how that affects the smoke. But the engine seems to be running fine. Is the white smoke simply steam?

[Ron Hill]

Free : You need to run you engine at operating temp for at least 10 minutes for the reasons mentioned.
Years ago I wrote that at a fabric store a few$$ will buy you enough to last a lifetime!  It is easier to glue the ends than sew it together.

Les : Most diesel engine books list white smoke causes as : 1. Poor Atomization of fuel  2. Poor Compression  3. Water in the fuel (small amount)

A few thoughts

[Ken Juul]

Paul,
If you are getting soot on the transmission, I would be looking for an exhaust leak.  But you need to differentiate between soot and dirt trapped from normal engine blow by.  Most of our engines are 20+ years old and run dirty.  Even if you re-ingest the blow by, it is the nature of the beast.  I have plumbed my blow by into the inside of the air filter.  Even so, after a season, the outside of the foam filter is black.

Les, If you think your fuel is ok, then it may be time for new injectors.  It is usually cheaper to buy new ones at a kubota dealer/tractor supply than have them cleaned.

[Paulus]

Ken, would a slipping transmission create more soot or excess fuel going through the engine?  Engine running at normal(2400rpm) but the boat is not going the normal speed?  Transmission has been taken out and is being repaired.  
The timing and valves will be checked in the spring time.  Injectors were rebuilt 4 years ago.
Paul

[Ron Hill]

Paul : I don't believe that a slipping transmission is a factor in more soot or extra fuel consumption, if the same rpm is used - boat speed would be lower though.