[C320-list] Black smoke with 3GM30F

[Joseph A Tamucci]

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