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Multiple 350 Q problems

S

Scott Bowlick

New member
Having a hard time with my port engine (33' CC Coho). I installed a brand new Edelbrock 1409 on both engines, along with new Sierra w/f filters and had the mechanical Carter pumps rebuilt. Starboard is running like a sewing machine, but port is stalling at idle when putting a load back on it (like returning to marina and close quarter maneuvering) and running rough. Noticed occasional sputter at cruising RPM.

Both engines have electronic (Pertronix) ignition. I replaced the flat cap and rotor-no improvement. Had a buddy check timing-which was off-and advance to 4 @ 600-800 RPM. No improvement. Started on fuel system-noticed fuel dripping from the primaries at idle. Checked floats, needles and seats-all ok. Adjusted floats down-no improvement. Swapped carbs-flooding condition on the port engine remained.

Yesterday I noticed spark is jumping the boot at the plug on one of the cylinders. Still need to pull that plug and inspect. I'm afraid of what I'll find.

Oh, and.....emulsified oil is showing up in the bilge. Now, I've got a slow leak from a seacock and I have dripping shaft logs, so there is always water in there. I also found a source of leakage, either from the fuel pump adapter or the circulating water pump fitting attached to the block on the timing chain end of the engine. But would oil drips into water turn creamy without being agitated mechanically?

So...are all these issued connected or do I have separate problems? Would a non or mis-firing cylinder cause an erratic fuel demand, resulting in the flooding carb? The rough running has always felt like an ignition problem which is why we started with rotor, cap and timing.

I will replace the ignition wire and inspect the plug. Anything in particular I'm looking for?

And just for fun, I went to start starboard to make sure the swapped carb was ok. I got a half a crank and then no battery. Parallel switch did nothing. I inspected the battery-it was buzzing and bubbling water or acid. Why do we love boats?
 
Scott Bowlick said:
  1. Both engines have electronic (Pertronix) ignition.
  2. I replaced the flat cap and rotor-no improvement.
  3. Had a buddy check timing-which was off-and advance to 4 @ 600-800 RPM. No improvement.
Started on fuel system-noticed fuel dripping from the primaries at idle. Checked floats, needles and seats-all ok. Adjusted floats down-no improvement. Swapped carbs-flooding condition on the port engine remained.
Click to expand...

  1. Pertronix as in the retro fit kits... or a completely new system???
  2. flat cap as in the old Mallory distribors..... or as in the Delco version????
  3. If these are old existing ignition distributors, you may want to verify that the advancing systems are working as they should be.

    Setting BASE or Initial advance is OK and is necessary......, but you really need to be checking to see what the progressive and TA (total advance at the correct RPM) are doing.
    BASE is BASE... we fire up on BASE, and we idle on BASE.
    Your progressive and TA are much more important than BASE will ever be.
    (see your OEM specs for this)


You'll need to mark off the harmonic balancers up to approx 35*.
Mr. Gasket (and a few others) offer a timing decal that makes this easy.
The decal must be correct for the diameter of the balancer.

Now you can strobe the timing marks at the progressively higher RPM ranges to the Full-In RPM.



.
 
Last edited:
thanks for reply! Yes, retro kit (prior owner installed). Mallory distributor, original. Ok, the manual really only discusses setting the base timing but we can see what she's doing in the upper RPM range....once we solve some of these other issues.
 
Scott Bowlick said:
  1. Yes, retro kit (prior owner installed). Mallory distributor, original.

  2. Ok, the manual really only discusses setting the base timing

  3. but we can see what she's doing in the upper RPM range....

  4. once we solve some of these other issues.
Click to expand...
OK.... that's good to know.

  1. The old Mallory flat cap distributors haven't been produced for years. This means that yours could be ____ years old.
    Who knows how well the mechanical advancing systems are working by now.
    A bit of rust on the flyweight return springs..... a bit of rust on the flyweights themsevles...... and you may have an incorrect advance.

  2. Most OEM manuals will spec out the TA. If you're using the Seloc or Clymers...... these specs may not be listed. :mad:

  3. What numbers are you seeing, and equally important, at what RPM?
    Just an FYI.... TA numbers are meaningless without an associated RPM.

  4. Scott, what I'm suggesting is that this may be your issue.
    An incorrect advance can raise it's ugly head in one of several ways.
 
UPDATE-#3 plug had 4 cracks in it! I replaced them all plus wires. Seems to have cured the flaky fuel issues. Now to set the timing and adjust the idle. Rick-thanks for the input. My distributors were rebuilt a few years ago according to PO paperwork. My boat neighbor had a buddy that can "power time" a marine engine. Apparently he sits in the engine compartment while we bring her up to cruising RPM and times it. Might be worth some pizza and beer to find out.
 
Scott Bowlick said:
UPDATE-#3 plug had 4 cracks in it! I replaced them all plus wires. Seems to have cured the flaky fuel issues.

Now to set the timing and adjust the idle. Rick-thanks for the input.


  1. My distributors were rebuilt a few years ago according to PO paperwork.

  2. My boat neighbor had a buddy that can "power time" a marine engine. Apparently he sits in the engine compartment while we bring her up to cruising RPM and times it.

  3. Might be worth some pizza and beer to find out.
Click to expand...


  1. If these were truly rebuilt, he should have a print-out of the actual advance curves.
    If not..... I'd be very suspicous, and I'd not trust this information.

  2. I'm trying to compose myself here, and I'm finding it to be difficult.


    NEVER, NEVER, NEVER, "power time" a gasoline Marine Engine! :mad:
    The human brain, eyes, ears can't accurately evaluate when the TA is correct, and/or if it's occuring at the correct RPM.
    This is why we rely on the years and years of R&D by the Marine Industry. They have clearly provided these specs for us.
    Our job is to follow their specifiactions.
    Short of over-heating and/or no oil pressure, "Detonation" is the Marine Gasser's worst enemy.


  3. Might be worth an A$$ Chewing, especially if this guy is doing this often.
 
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