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Old 18-02-2008, 11:41   #16
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Yes that is a good place to start and seems to be a common problem.
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Old 19-02-2008, 21:09   #17
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Here are a few things to check.

Normally this is due to a air to fuel ratio imbalance, either the fuel system is delivering too much fuel into the engine or there is not enough clean air (oxygen ) a few things to look for :
  • Faulty injectors (Not likely but possible)
  • Faulty injector pump (Poss bad return spring, you would likely be showing some other symptoms)
  • Dirty air cleaner ( I am pretty sure you have checked this)
  • Turbocharger or intercooler faulty (Would be my first guess. Neutral doesn't require the boost to make power that a load does. See if you have any way to hook up a boost gauge to the turbo. The elbow could indeed be bad. The spare you have on the boat may also be a bad, a part that someone saved. Check the exhaust from the engine to the turbo for any leaks, not hard to find but don't burn your hand. Replace the elbow and see if it changes. Turbo's do sometimes fail, usually caused by lack of oil or overheating.)
  • Problems within cylinder head, valves clogged up due to faulty EGR (exhaust gas recycling unit, If you have tried everthing else)
  • prop shaft or prop (Possible but not my first guess. I think you would pick up some excessive heat or vibration on the shaft if the bearing had failed. If you grounded you could have bent a prop, but that bent should be visible.)
I am not a marine mechanic, but have played with diesels for a long time.

Hope this helps....Good Luck
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Old 27-02-2008, 20:42   #18
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No Obvious Cause Yet...

I pulled the exhaust elbow - no big carbon build-up at all. Yes there was some but nothing real bad. Exhaust side of the turbo has a blob of carbon buildup about the size of a quarter - not on the blades but near the flange that mounts the exhaust elbow.

I pestered the local Yanmar expert for about an hour and we reviewed the entire scenario and history. I also spun a known good turbo unit he had in the shop and it feels the same as mine. Don't think it's the turbo at all.

One thing I had not done is change the secondary fuel filter - the 2 micron unit mounted on the engine. I will change that before we launch again.

I remember that after we first took delivery and made the trip from New Orleans to TX, we had black soot in the wake. We made 7 kts at only 2200 RPM, and I honestly cannot remember if the engine ever spun up to its rated max of 3600.

I'm going to gather the prop specs and tranny ratio and go figure out if I have the right prop.

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Old 20-05-2008, 08:04   #19
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And Now the Root Cause is Known...

The gods have smiled upon me.....

Shafting is good, turbo was fine. I spent $150 to have my prop re-pitched from 21-17 to 21-12 and voila!! No black smoke, cruising RPM (2300) makes 6.5 knots. I may be a tad under-pitched but man do I love not having that sooty residue floating in the wake!

Engine runs cooler now too - go figure. "Check the simple things first" is becoming my new mantra...

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Old 20-05-2008, 08:12   #20
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Dirty air cleaner?
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Old 20-05-2008, 09:23   #21
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I don't think you've found the problem. If you were making full RPM with 17" of pitch and can now only make full RPM with 12" of pitch, something upstream of the propeller changed. Then engine running better with less load proves little.

Brett
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Old 20-05-2008, 12:09   #22
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Originally Posted by LtBrett View Post
I don't think you've found the problem. If you were making full RPM with 17" of pitch and can now only make full RPM with 12" of pitch, something upstream of the propeller changed. Then engine running better with less load proves little.

Brett
Original problem was that I could NOT get full RPM prior to reducing the pitch. Also had heavy black smoke.
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Old 20-05-2008, 14:38   #23
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I cannot reach full RPM as before. I am investigating shafting / cutlas bearing as we speak (gonna pull the shaft).

This appeared rather gradually. Smoking gradually worse, now heavy and lots of black soot floating in the wake.
I'm confused...

If re-pitching solves you issue, cheers to a cheap fix!

Brett
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Old 20-05-2008, 15:03   #24
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Yeah... turns out that fouling really aggravates an over-propped condition. And we recall seeing the soot in our wake from the very first trip we made on a clean bottom.

So yes - cheap fix!
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Old 21-05-2008, 01:58   #25
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And hence my comments often stated, the prop has to be correctly pitched. It is essential.
So have you noticed other things like the boat seemingly being a little more "lively" in tight manourvering ?
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Old 21-05-2008, 06:09   #26
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One of the nice advantages of the Max Prop is the ability to set the pitch to reach WOT. Seems like I've met lots of folks that were over pitched and did not realize they were harming the engine by lugging it. If you can't get with WOT (within ~20%) better start looking. The prop is the easiest starting point.
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Old 21-05-2008, 07:08   #27
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....So have you noticed other things like the boat seemingly being a little more "lively" in tight manourvering ?
Well yes and no. I confess to having made a true "Captain Ron" landing as I became aware - too late of course - that I've not as much backing power as before. I'm happy to report that the maneuver came out splendidly with no crunching of the dock. But my engine revs were way too high trying to get her to stop.

We all had a good laugh about the Capt Ron landing - properly executed I might add...

The only thing missing was the free food and open bar waiting for us on the dock... darn it
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Old 21-05-2008, 13:41   #28
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But my engine revs were way too high trying
The beauty of diesel is that you can't have "way to high" revs. It is governed, so protected. If you have lost "bite" in the water, you can (if you can) swing a larger diameter. The largest diameter with the correct pitch is best to gaining the 'grip" with traction in the water. It is rare to find over spec'd diameter props on sail boats, as hull restraints are the usual that stop you from applying a too large a prop.
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Old 21-05-2008, 13:44   #29
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Alan - what I meant was that I was making way too much headway and had to back down too hard to save us.... not a real "finessed" landing for me
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