[C320-list] exhaust mixing elbow

[Robert Seastream]

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
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