[C320-list] Brown Smoke from Exhaust

[Dingo Is Talent]

HI Annie
I had exact same problem recently and it WAS the exhaust elbow where sea
water mix in ...corroded so bad put back pressure on exhaust causing black
brown smoke.
Replaced...now perfect
DINGO Down Under - Perth Western Australia 
1150

-----Original Message-----
From: c320-list-bounces at lists.catalina320.com
[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Annie Bennett
Sent: Monday, 23 September 2013 9:08 PM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] Brown Smoke from Exhaust

Can anyone give me a pointer on the meaning of brown smoke from exhaust.

Today was my second day out on Topcat after a month overseas.  Topcat's
engine was serviced just before we went away.  This morning before going out
I checked the oil and all was fine.  I thought the coolant might be a bit
low in the visible container and called the mechanic to see if he could
change it as I noticed in the engine log it hasn't been changed for a while.
The wind was light so I motored for a couple of hours - all fine - then
sailed with the engine off for another hour and only turned the engine back
on for the last 15 minutes for getting the sails down and coming into the
mooring.  In the last 5 minutes I noticed some white smoke.  It must be
smoke not condensation as it was a very warm day and the engine was warm.
There was no smoke earlier in the day.  

After my guests had gone ashore I decided to turn the engine back on to test
it, initially nothing, just the normal water, but then white smoke came out
- no smell.  Still In neutral I turned the revs up to 28 and then brown
smoke started coming out and there was a faint oily residue on the water
that I think but am not certain came from Topcat.  I turned the engine off.
I wanted to double check before calling the mechanic that I really had a
problem and turned the engine back on, still in neutral revved again.  First
nothing, then  white smoke then quite a lot of brown smoke again but this
time a slight burning rubber smell.  I've turned it off and the mechanic is
hopefully coming tomorrow afternoon.  Plenty of water is coming out as
normal.  The impeller was changed in the service in August and today is only
the second time I've been out since the service.  Someone at the marina
wondered if the smoke could be caused by my fouling the propellor on
something in the water but he changed his mind when I said the brown smoke
came out when revving in neutral.  Does anyone have any ideas that might
help the mechanic.  I've done about 1000 hours.  My googling suggests it
might have something to do with fuel injectors.  If so is this a big /
difficult / time consuming problem for a mechanic to fix?  I'm hoping not as
I have a charter booked for a birthday on Wednesday and I'm hoping I won't
have to cancel and let them down.  Ive never had a problem with smoke of any
colour before.

Thanks in advance to anyone for their help / advice.

Kind regards
Annie Bennett
Topcat #1073