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Old 01-14-2016, 09:31 AM   #41
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The descriptions of how soon after the relaunch are not specific enough.


I don't see alignment causing this. You need to have a diver inspect the props for problems. Doesn't matter if the bottom was cleaned two weeks ago. something happened and all the armchair speculation wont identify the problem.


You could ask the yard for a quick haul and inspect.
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Old 01-15-2016, 06:28 AM   #42
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"Ironically, I got shaft and strut work done to correct what was said to be a very critical misalignment issue. Now, when the engine is off the prop spins quite freely when in neutral."

Any chance the repair gave you more RPM and you are now in a range that does overload the prop?

"something happened and all the armchair speculation wont identify the problem"

True, but most boat yards are very limited in problem solving, Remove and Replace is far more profitable .

Their yard "mechanic" may be grand with gas IO but is usually hard pressed to diagnose a diesel operation.

IF 90% of the vessels there are like yours , you have a better chance at solving a problem.

Getting even speculation from the 1000 years of experience on a board is better than guessing

Make a list , (of questions) check it twice,,,
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Old 01-15-2016, 10:11 AM   #43
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Maybe the yard made a mistake and put someone elses prop on. It's happened before.
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Old 01-15-2016, 11:25 AM   #44
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Having just been through a four month issue with running gear ourselves it is easy to envision the possibility that the additional load your engines are seeing was caused by actions the yard took to correct whatever your initial problems were. This could have resulted in increased friction due to misaligned engines, misaligned struts, incorrectly sized cutless bearings, bent shafts, shaft couplers not properly aligned with the shafts or mated to the transmission output flange, improper clearance between the shafts and the insides of the packing glands, bent shaft log hoses, or something else putting enough pressure on the components to increase the drag and thus the load on the engines causing them to work too hard, hence your black smoke.

Our situation had nothing to do with alignment or engine load but I know how easy it can be for several things to change when one thing in the system is changed or worked on.

You mention the yard found problems with your "struts and driveline." Does this mean both sides or just one?

Do you know if your shafts were easy or relatively easy to turn by hand from inside the engine room before, and if they were, are they still that way? If there is no change in the effort needed to turn them, that does not mean that misalignment of some sort is not the culprit. But if there is a difference in the effort to turn them that can be a clue that misalignment of something could be the problem.

Unless you had the props worked on they should be the same as they were before your haulout. And if they were clean when the boat went back into the water it would be surprising if both of them got fouled enough (depending on how long it's been since your haulout) to have such a severe effect, although with boats one soon learns to never say never.

Black smoke notwithstanding, does the boat feel like it's doing the same speed and going through the water in the same way at the same power settings now as it has in the past? Don't know about your boat but when ours is nearing the need for a haulout with significant bottom, prop and rudder growth we can feel the difference in the hull's movement through the water, to say nothing of seeing it on the knotmeter.
Marin:

Your reply is very much spot-on. The yard corrected some very egregious misalignment and shoddy repair issues. They surmised that the boat was at one time grounded and that the subsequent work to fix the damage was done as poorly as it possibly could have been. The yard and the mechanic involved are viewed as being the best in San Diego.

I had the props pulled and taken in to see about the pitch, etc. Lo and behold, they found that the props were not the proper size for the engines. The feeling is that, after the right props are put on, coupled with the strut and driveshaft work that was done that I will have a boat that will perform quite well.

Thanks for your input!

Best regards,
JE
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Old 01-15-2016, 12:11 PM   #45
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So the prop pitch was changed while at the yard? What was the pitch before props were adjusted, and what was the pitch after?

Props are not selected for the engines, they are selected for the boat and engines. Not a simple task to select the correct prop pitch.

This is an important detail that I don't recall being revealed til now.
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Old 01-15-2016, 12:20 PM   #46
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Marin:

Your reply is very much spot-on. The yard corrected some very egregious misalignment and shoddy repair issues. They surmised that the boat was at one time grounded and that the subsequent work to fix the damage was done as poorly as it possibly could have been. The yard and the mechanic involved are viewed as being the best in San Diego.

I had the props pulled and taken in to see about the pitch, etc. Lo and behold, they found that the props were not the proper size for the engines. The feeling is that, after the right props are put on, coupled with the strut and driveshaft work that was done that I will have a boat that will perform quite well.

Thanks for your input!

Best regards,
JE
So the previous props were removed and different or reworked props were put back on????? If that is the case, that is your answer!...without a doubt!!! The "excellent" yard/mechanic screwed up by putting on the wrong pitched props!!!
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Old 01-15-2016, 12:38 PM   #47
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The what and when is a little fuzzy here.....
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Old 01-15-2016, 02:01 PM   #48
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So the prop pitch was changed while at the yard? What was the pitch before props were adjusted, and what was the pitch after?

Props are not selected for the engines, they are selected for the boat and engines. Not a simple task to select the correct prop pitch.

This is an important detail that I don't recall being revealed til now.
Ski:

I did not say that the pitch was changed while at the yard, or at least I did not mean to. The repair outfit that I am working with took the John Deere Manuals that I had and all of the other salient information about the boat to the propeller shop that we are working with. After reaching out to the local John Deere rep (who then checked with John Deere directly) it was determined that the prop was not of the proper size. As for the pitch settings, I would surmise that they are going to go through the proper process for determining this. However, to be on the safe side, I shared your observations with them to make sure that all is in order with respect to the new props that I am going to buy.

Thanks for you input.

Best regards,
JE
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Old 01-15-2016, 02:23 PM   #49
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All of a sudden (in somewhat colder than normal weather) we have had black smoke come out of our exhausts when under full load. We are being told that our props might not be set up properly (pitch, etc.). Being very much mechanically challenged, I am hoping that somebody might be able to shed some light on this for me. We've never had the smoke problem before; but then, we've never operated the boat in cold weather.
So this is the opening post. Quite a story change. I'd urge you to contact Tony Athens to see if the guys you are using are the right ones.
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Old 01-15-2016, 02:50 PM   #50
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Ski:

I did not say that the pitch was changed while at the yard, or at least I did not mean to. The repair outfit that I am working with took the John Deere Manuals that I had and all of the other salient information about the boat to the propeller shop that we are working with. After reaching out to the local John Deere rep (who then checked with John Deere directly) it was determined that the prop was not of the proper size. As for the pitch settings, I would surmise that they are going to go through the proper process for determining this. However, to be on the safe side, I shared your observations with them to make sure that all is in order with respect to the new props that I am going to buy.

Thanks for you input.

Best regards,
JE
It is not important whether the props were changed while at the yard, it is important that the props were changed in the interval between "engines not smoking" and "engines smoking".

If you change props, the performance of the boat and engines will change, sometimes for the better, sometimes for the worse. Changing props is a bit like changing gears on a car going up a mountain. It changes how far the boat advances per engine revolution.

The best way to select props is to do a sea trial with old props and clean bottom, gather the data, THEN decide on diameter/pitch for new props. Even then it is an imperfect calculation. Props are a bit of a "black art".

Using boat data, engine data and gear data from boat literature to select props will provide much poorer results than selecting props based on sea trial data.

I understand this stuff is not your forte, thus the explanation.

At this point, you need to do a sea trial with a mechanic and phototach. Go to full power and get accurate rpm data. If rpm is low, props have too much dia and/or pitch and that is the cause of the black smoke.
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Old 01-16-2016, 09:06 AM   #51
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Before props pitch is adjusted engine valve adjustment should be checked, especially if it hasn't been done within the engine manufacturer's specified interval, injector nozzles inspected, and exhaust back pressure should be checked, again especially if this hasn't been done in some time. Prop pitch should be adjusted only after it is confirmed the engine is in good working order, and it meets installation requirements, again especially back pressure. Excessive back pressure robs horsepower and is tantamount to increased prop pitch. Reduced pitch can account for or mask excessive back pressure, however, it means the engines aren't delivering their rated hp to the props. Other out of tune items such as miss-adjusted valves or fouled injectors can have a similar effect. The quick fix for many builders and yards is to rush to prop adjustment, but that's frequently not the culprit.

Props are not matched to engines and application using manuals, they are matched using a prop-calculator, one is available on the boat diesel website, to get close to what's needed, and then a sea trial to fine tune if necessary. Sea trials should be carried out with a full cruising load and the engine must be run at wide open throttle for at least a few minutes until rpm stabilizes to analyze the match. Ideally, engines should turn up to and slightly over, 25-50, the rated rpm, to account for added weight and drag that develops or is added over the vessel's life. Bottom line, black smoke is most frequently the result of an over-load, which could be caused by a fouled or incorrectly sized prop.
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Old 01-16-2016, 09:09 AM   #52
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IMO you need to go back to the yard tell them what's you see and allow them to asses the problem and search for the cause. Sure sounds like over propping but how they got that way is very unclear from the discussion.
This is an important issue but not a big deal for an experienced yard to analyze and fix.
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