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Here is another possibility - you inadvertently added diesel with low cetane. You could try a cetane additive to determine if it makes any difference. Did you buy the fuel from a different source than you normally do?
 

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Discussion Starter · #22 ·
This O'day 35 has the original 1986 Florida Marine Tanks 35 gallon tank;


I use about 20 gallons of diesel per year, and always top it off from my marina before winter layup, so it has never been fully drained. I tape the vent closed, and close the fuel shutoff during winter layup.
 

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I installed new injectors last winter, replaced the valve cover gasket (not needed), and upgraded the heat exchanger from the 2" to the 3"... nothing that should have mussed up the timing though.
The more I think about the intermittent nature of the problem the more I think it may be an injector problem. When knocking and putting out excess smoke one of the injectors may not be producing a proper spray pattern, due to debris or water?

If it was fuel starvation I think you would just lose power. Kind of sounds like fuel may be puddling up? Are there any indications that excessive blow by vapors can be collecting in or near the intake tract?

Having the injectors checked by a shop would be easier than pulling the head?

James' comment about cetane additives would be an easy try. Or maybe a heavy duty "cleaner" additive? I used to use this in my VW diesels & never had any fuel related problems:

DIESEL KLEEN庐 +Cetane Boost庐: Max HP Formula ? use during non-winter months for the ultimate in performance.

I am sure there are lots of different additives that may be as good or better?

Paul T.

Edit: Just saw your picture, the tanlk has been around for a while.:D

I did some tests with the Power Service additive a long time ago. Put some diesel in a coffee can, added a little water to it, then added the additive & the water was no longer visible. A tank that old may very well have some water in it. However, a good filter/separator should catch it. Some units have a clear bowl on the unit allowing you to see water or debris.

Paul T
 

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The more I think about the intermittent nature of the problem the more I think it may be an injector problem. When knocking and putting out excess smoke one of the injectors may not be producing a proper spray pattern, due to debris or water?

If it was fuel starvation I think you would just lose power. Kind of sounds like fuel may be puddling up? Are there any indications that excessive blow by vapors can be collecting in or near the intake tract?

Having the injectors checked by a shop would be easier than pulling the head?

James' comment about cetane additives would be an easy try. Or maybe a heavy duty "cleaner" additive? I used to use this in my VW diesels & never had any fuel related problems:

DIESEL KLEEN庐 +Cetane Boost庐: Max HP Formula ? use during non-winter months for the ultimate in performance.

I am sure there are lots of different additives that may be as good or better?

Paul T.

Edit: Just saw your picture, the tanlk has been around for a while.:D

I did some tests with the Power Service additive a long time ago. Put some diesel in a coffee can, added a little water to it, then added the additive & the water was no longer visible. A tank that old may very well have some water in it. However, a good filter/separator should catch it. Some units have a clear bowl on the unit allowing you to see water or debris.

Paul T
Thought maybe you might have missed the edit.

Paul T
 

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Molecules of water going thru the injector tip tear helll out of the tiny holes Bad spray pattern can blow holes in the piston top. Sounds like knocking until the serious blowby starts. Some fuel additives can carry the water to places it's not meant to be .Catch it early.
 

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Molecules of water going thru the injector tip tear helll out of the tiny holes Bad spray pattern can blow holes in the piston top. Sounds like knocking until the serious blowby starts. Some fuel additives can carry the water to places it's not meant to be .Catch it early.
I have read about but never had the water/injector problem, that I know of. If there is water in the tank It would be good to get it out before it goes into/thru your filter/separator. From the picture it looks like there is a port cover/cap that may be able to remove on the left side. If so, maybe put a piece of hose into the forward left corner & use a pump to pull it out. Suggest you not try to siphon it by mouth. I swallowed a LARGE mouthful of gasoline doing that.

Perhaps you could weight the boat so that the forward left corner of the tank the lowest. I think most pick up tubes are not right on the bottom of the tank. So if you are picking up water, there may be a fair amount of water in the tank. After removing the tank cap, you may be able to see any water rolling around in there?

A good filter/separator should catch any water or debris? "Should" is the key word. :D

Paul T
 

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Yes the decreasing oil pressure has been a long running mystery. It starts out at 50 PSI, the gradually drops, but never so low as to sound the alarm. It has done this for the past 2 years, possibly longer.
It's probably not as much of a mystery as you would think.

IMHO it is probably nothing more than a failing oil pressure sender unit. This is quite common - I have had it on my own boat and recently had exactly the same thing on the wife's car. On the boat it went on for a few years getting gradually worse. On the car it went from normal to "no pressure" in about a month.

As the engine warms up the resistance in the sender changes and indicates lower and lower pressure but never sets off the buzzer. That's because the buzzer has its own sender and doesn't use the signal from the gauge sender so is sensing the "real" pressure which is probably normal.

For the cost of a new sender unit, the peace of mind is worth it.
 
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Discussion Starter · #31 ·
I think that's one of them Tadslack steering systems.
That pic was taken 4 years ago; before I removed the steering quadrant and dropped the rudder so that I could replace the cutlass bearing and prop shaft. Upon re-installation, everything was tightened appropriately.

If you were to see this view today, you wouldn't recognize the place, except for the original, oxidized, fuel tank.:)
 

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Discussion Starter · #32 ·
It's probably not as much of a mystery as you would think.

IMHO it is probably nothing more than a failing oil pressure sender unit. This is quite common - I have had it on my own boat and recently had exactly the same thing on the wife's car. On the boat it went on for a few years getting gradually worse. On the car it went from normal to "no pressure" in about a month.

As the engine warms up the resistance in the sender changes and indicates lower and lower pressure but never sets off the buzzer. That's because the buzzer has its own sender and doesn't use the signal from the gauge sender so is sensing the "real" pressure which is probably normal.

For the cost of a new sender unit, the peace of mind is worth it.
THAT makes perfect sense! It is quite unnerving to have 50 PSI at the outset, and < 10 after about 3 hours motoring...
I'll be installing a new sender soon!
 

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It's probably not as much of a mystery as you would think.

IMHO it is probably nothing more than a failing oil pressure sender unit. This is quite common - I have had it on my own boat and recently had exactly the same thing on the wife's car. On the boat it went on for a few years getting gradually worse. On the car it went from normal to "no pressure" in about a month.

As the engine warms up the resistance in the sender changes and indicates lower and lower pressure but never sets off the buzzer. That's because the buzzer has its own sender and doesn't use the signal from the gauge sender so is sensing the "real" pressure which is probably normal.

For the cost of a new sender unit, the peace of mind is worth it.
Also, a mechanical gauge should be fairly reliable.

Paul T
 

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Also, a mechanical gauge should be fairly reliable.

Paul T
Yes it would but that's a whole new project . . . . where would I put one on my boat? Don't actually know.
 

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Discussion Starter · #35 ·
The new sender is on order from Amazon...

What happened to when employees actually had to know something about auto parts? I stopped at Pep Boys, AutoZone, and Advance Auto, and they all ask what kind of car. "It's not for a car...." Then we can't help you. Bottom line is if they can't look it up in a book, they're not interested in helping you out.
 

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Yes it would but that's a whole new project . . . . where would I put one on my boat? Don't actually know.
I have installed a steel "T" fitting in the original sender hole, one side for the electrical sending unit, the other side for the small, what appeared to be plastic or nylon, hose that went to the mechanical gauge.

Or, one could just temporarily hook up the mechanical gauge to verify the accuracy of the electric gauge.

IIRC, I think I have read about mechanical & electric gauges operating on one sender.

Paul T
 

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T'ing the output at the engine block is the way to go. The little oil line can be short and run to a gauge close to the engine,(not on it due to vibration) The other side of the T holds the electric sender. If you trust your new sender the T can go to an off/on sender for alternator field and a solinoid to drain/prevent filling exhaust riser.
 

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I have installed a steel "T" fitting in the original sender hole, one side for the electrical sending unit, the other side for the small, what appeared to be plastic or nylon, hose that went to the mechanical gauge.

Or, one could just temporarily hook up the mechanical gauge to verify the accuracy of the electric gauge.

IIRC, I think I have read about mechanical & electric gauges operating on one sender.

Paul T
Hey Paul, without wanting to pull the ring out of this, it's not about the connections to the engine, that's the easy part.

It's about where to put the gauge. It's not going to fit the original panel - or let's say it certainly won't on a Yanmar panel, maybe it will on a Universal's panel.
 
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Hey Paul, without wanting to pull the ring out of this, it's not about the connections to the engine, that's the easy part.

It's about where to put the gauge. It's not going to fit the original panel - or let's say it certainly won't on a Yanmar panel, maybe it will on a Universal's panel.
Ah, understood, space. One thing always seems to lead to another, turning into a big project. :)

Paul T
 

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Discussion Starter · #40 ·
T'ing the output at the engine block is the way to go. The little oil line can be short and run to a gauge close to the engine,(not on it due to vibration) The other side of the T holds the electric sender. If you trust your new sender the T can go to an off/on sender for alternator field and a solinoid to drain/prevent filling exhaust riser.
I actually think that the solution on my boat is better. There is a hydraulic high pressure hose screwed into where the oil pressure switch would normally go, and this is run to a bulkhead in the engine room. There is a "T" fitting on the other end of the hose, on the bulkhead, and an oil pressure switch, and oil pressure sender on the T. This reduces the mass connected to the vibrating engine by a pressurized T fitting, and isolates the switches from the effect of vibration.

Here is an OLD picture, in which you can see the hose, pressure switch, "T", and sender to the right of the OLD Sea Ranger battery charger (now gone);
 
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