[C320-list] Black smoke with 3GM30F

[JJ Morrison]

Could be your exhaust elbow has carboned up. Exhaust restriction often results in the symptoms you describe.CheersJohnM1999#574

> From: jtamucci at comcast.net
> To: c320-list at lists.catalina320.com
> Date: Sun, 17 Aug 2014 15:07:01 -0400
> Subject: [C320-list] Black smoke with 3GM30F
> 
> Most of this season, the boat has been sitting on the mooring with not much
> sailing or motoring.  In fact I still have the same tank of diesel I put in
> last October 2013.  I also have a 3 blade Martec feathering  prop.  At the
> beginning of the season, the boat ran great and I could get up to 7 knts at
> 3400 RPM and no smoke at all, so the prop pitch seemed perfect.
> 
> Recently I noticed a fuel leak from the secondary filter so I bought a new O
> ring but the leak around the cap continued and when I tried to screw it ona
> 3rd time I lost the prime and even after bleeding the secondary could not
> get the engine to start.  I had the yard mechanic fix it and they had to
> bleed the injectors. 
> 
>  
> 
> I went on vacation for a couple weeks and same back. Now the engine starts
> fine and will freely rev up to 3600 RPM in neutral.  When I put it in
> forward however and give it some throttle, very little response and black
> smoke comes out the exhaust.  Max RPM was 2000 with lots of black smoke and
> soot.  It works much better in reverse but still some black smoke.  So it's
> a classic overload problem due to a fouled prop or drivetrain?
> 
>  
> 
> So I dive on the prop but very little fouling but I scrap it clean anyway.
> The haul is also clean. Same problem.  So I go down and repitch the prop a
> couple times (it has adjustment screw).  The 1st time I repitched, the smoke
> went away but I could only get up to 4.9 knts at max RPM of 3100.   After a
> couple more adjustments I can get up to 3000 RPM and 6 knts before it starts
> smoking at full throttle which gives me 3100 RPM.  The shaft spins easily by
> hand turning at the engine, and the prop seems to be feathering fine.  The
> engine is not overheating either, and very little vibration in the
> drivetrain.  So I was able to improve things but still not like before.
> 
>  
> 
> So after all that, my question to you is, is it still an driveshaft overload
> problem, or could it be an engine problem?  Could the mechanic have screwed
> anything up by bleeding the injectors?
> 
>  
> 
>  
> 
> Joe Tamucci #619
> 
>  
>