[C320-list] Fwd: Re: exhaust mixing elbow

Sat Sep 20 12:46:13 PDT 2008

There have been a number of postings regarding clogged exhaust elbows.  The 
Yanmar operator's manual may offer a key to reducing this problem:

Article 3.3.5 Stopping the Engine

Stop the engine in accordance with the following:

1.  Put control handle in neutral.
2. Be sure to race the engine before stopping it. (See 3.3.4 (7)
3.  Cool down the engine at low speed (approximately 1000 rpm for about 5 
minutes).

Article 3.3.4.(7):

When operating the engine at low speed for long periods of time, race the 
engine once every 2 hours.
Note:  Racing the Engine --- With the clutch in Neutral, accelreate from the 
low speed position to the high speed position and repeat theis proces about 
5 times.  This is done to clean out carbon from the cylinders and the fuel 
injection valve.  Neglecting to race the engine will result in poor exhaust 
colour and reduce engine performance.

I don't see where high speed is defined, and while it doesn't address 
exhaust elbow directly, if the engine is building up carbon and putting out 
the wrong colour exhaust, it stands to reason that carbon present in wrong 
colour exhaust may well be plating out in the exhaust elbow, eventually 
clogging it.

If like me, you have to run the engine slow in no wake zone and while 
docking, the carbon may build up if above procedure is not followed. 
Personally, I use a little different approach, for the high speed racing, I 
let the engine run for a few minuties (5) at ~1800 -2000 rpm before shuting 
down to clear the injectors.  Thus far no problem, but it may be too early 
to tell.

Dennis Harris
C320 #694

----- Original Message ----- 
From: "Crosby Roper" <vmdatsea at hotmail.com>
To: <c320-list at catalina320.com>
Sent: Saturday, September 20, 2008 12:02 PM
Subject: Re: [C320-list] Fwd: Re: exhaust mixing elbow

Carl,

The mechanic replaced my elbow saying it was completely clogged. Yet to 
receive the bill... What is the procedure for cleaning the elbow? I'd like 
to avoid replacement in future if possible.

Crosby Roper, VMD

> Date: Fri, 19 Sep 2008 20:47:48 -0400> To: C320-List at catalina320.org> 
> From: c320 at suddenlink.net> Subject: [C320-list] Fwd: Re: exhaust mixing 
> elbow> > Crosby,> > My experiences and operating procedures are similar to 
> Bob's and Allan's. > I try not to motor under 2400 rpm for extended 
> periods of time and if I > do, I run the engine up to 3400-3600 rpm for a 
> few minutes every half hour > or so. I also add Algae-X to my fuel (adds 
> lubricity) even though we are > still able to get low sulfur diesel (NC 
> hasn't mandated the ultra low > sulfur diesel yet for boating or off-road 
> use).> > I did recently pull my elbow and exhaust line to the Aqualift 
> muffler, > thinking I might need to clean same. They looked great, just a 
> thin > coating of carbon. Pics are posted here...> 
> http://www.catalina320.com/gallery/album94> > Karl> > ------- Forwarded 
> message -------> From: "Robert Seastream" <robert.seastream at comcast.net>> 
> To: C320-List at catalina320.com> Cc:> Subject: Re: [C320-list] exhaust 
> mixing elbow> Date: Fri, 19 Sep 2008 20:12:57 -0400> > We have about an 
> hour run to get downriver and out of Portsmouth> harbor to offshore. We 
> run at 2400 for fuel economy, 3000 if we have> to hustle to make the 
> bridge openings. 3200 is the continuous max> rating for our Yanmar 3GM30F. 
> Once or twice a year, I run WOT (3600> rpm; coincides with the one hour 
> engine rating) for about 15 minutes.> Never had 'smoke' issues, however 
> our engine only has about 300 hours> on it. Engine temps range from 160 to 
> 180 degrees farenheit under> those respective conditions.> > Bob 
> Seastream> Intuition # 906> > On Sep 19, 2008, at 6:04 PM, Allan S. Field 
> wrote:> > > We make sure that every time we run the engine, we run at 
> 3,000 rpm> > for at> > least 5 minutes. 600 hours and no smoke although we 
> intend to pull> > and> > clean the elbow prophylactically this winter 
> regardless.> >> > Allan S. Field> > Sea Shadow - #808> > Columbia, MD> >> 
>  > -----Original Message-----> > From: 
> c320-list-bounces at lists.catalina320.com> > 
> [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Crosby> > 
> Roper> > Sent: Friday, September 19, 2008 5:42 PM> > To: 
> c320-list at catalina320.org> > Subject: [C320-list] exhaust mixing elbow> >> 
>  > Thought I'd pass this along for general lesson learned file. In july> > 
> on my> > way back from Catalina island to San Diego, I noticed that when 
> I> > ran the> > RPM's up to 3200, I got a bit of black/brown smoke from 
> exhaust.> > Since water> > tanks were full and there was a bunch of stuff 
> on board, I figured> > probably> > just overloading the engine was the 
> problem. On my next trip to> > catalina on> > Labor day, I noted smoke at 
> 3000 RPM. To make a long story short, the> > problem progressed rap[idly 
> over the next 30 hrs of engine use to> > the point> > where even at 2000 
> RPM i was seeing smoke. We limped back to the> > slip and> > called 
> mechanic ( to whom I had spoken while in Catalina and who had> > advised> 
>  > me that problem was likely a clogged exhaust mixing elbow and OK to> > 
> run> > engine at low RPM as long as it was not producing smoke.) He came> 
>  > out on> > Monday and problem was indeed exhaust mixing elbow. The engine 
> is 3> > years> > old and has about 220 hrs on it. He admonished me for not 
> using the> > boat> > enough (in front of my wife, which should work out 
> well for future> > sailing> > schedule) and for babying the engine. So, 
> for anyone else who tends> > to baby> > their diesel, run it frequently 
> and run it hard. But we already know> > that!Crosby Roper, VMD> > Tethys # 
> 1054> > _________________________________________________________________> 
>  > See how Windows connects the people, information, and fun that are> > 
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> http://clk.atdmt.com/MRT/go/msnnkwxp1020093175mrt/direct/01/=> >> > > > --  
>  > Karl Mielenhausen> Catalina 320 Hull 690> New Bern, NC
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