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Old 09-27-2017, 04:49 PM   #41
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I'll bet there is a little bit of an air intrusion issue. Once power is up, the air washes through without issue. Only shows up in weird ops like the hour idling. Tracking down the issue might be a bugger. If engine runs fine otherwise, I'm not sure I would put much effort into troubleshooting.
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Old 09-27-2017, 05:28 PM   #42
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You could leave it idling and sit in the boat and wait to see how long it will run before it quits, but personally I think that would be sort of dumb to do.


Yea - can you imagine the guff he'd get if he did it AGAIN?
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Old 09-27-2017, 05:46 PM   #43
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My engine gets air when my starboard tank gets lower than the lift fuel pump.

Not always but the engine will start and run norfmal, the 5 minutes outside the marina it will sputter and 2X it has died on me.

Tightened everything, next step is try electric fuel pump.

Been chasing it a bit for 2 years.
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Old 09-27-2017, 07:32 PM   #44
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Here you go - read Steve on this topic. Maybe his opinion carries more weight?

The Perils of Chronic Under-Loading | Steve D'Antonio Marine Consulting
And to add some balance

Quote:
To me, the easiest way to gauge whether slow speed running is detrimental over years and years of operation is to look at commercial fishing vessels with older designed engines from Detroit, Cat, Cummins, etc… Revisiting the “Detroit” mystique again, its longevity was built on engines rated to run at 1900-2100 RPM and above, but could only last for 30+ yrs when operated continuously at 1100-1600 RPM (again, well under 50% of rated HP)..These same engines in a “crew” boat used in the off-shore oil industry, would go through “top-ends” (or worse) just about yearly when run at close to their governor settings..The longest-lived engines that I’ve been involved with (hrs and yrs wise), have been engines in commercial or recreational trawler type applications run at 50% of rated HP or less.
(snip)
In closing, I’ll mention that although this topic is brought up quite often and many people preach that you’ve got to use a diesel hard if you want it to last, I’m still waiting to find one that was rebuilt before its time due to low speed use..Just the opposite seems to be always the norm.

https://www.sbmar.com/articles/low-s...arine-diesels/
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Old 09-28-2017, 07:02 AM   #45
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".The longest-lived engines that I’ve been involved with (hrs and yrs wise), have been engines in commercial or recreational trawler type applications run at 50% of rated HP or less."

What HP an engine is rated to do at WOT has little to do with service life at lower RPM.

Every engine has a graph that shows max power at lower RPM , it might be 215HP at 2100RPM , but down at 1500RPM it could be 100HP.

As long as a substantial percentage of that 100HP is used the engine will live fine.

If only a tiny percentage is used , slobbering becomes possible.

The best way to set up a boat is with a fuel map , the center of the efficiency bullseye is usually the sweet spot.
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Old 09-28-2017, 02:10 PM   #46
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".The longest-lived engines that Iíve been involved with (hrs and yrs wise), have been engines in commercial or recreational trawler type applications run at 50% of rated HP or less."

What HP an engine is rated to do at WOT has little to do with service life at lower RPM.

Every engine has a graph that shows max power at lower RPM , it might be 215HP at 2100RPM , but down at 1500RPM it could be 100HP.

As long as a substantial percentage of that 100HP is used the engine will live fine.

If only a tiny percentage is used , slobbering becomes possible.

The best way to set up a boat is with a fuel map , the center of the efficiency bullseye is usually the sweet spot.


Actual ex commercial fishing trawler plodding along in the dark now doing 7.5 knots @ 1150 rpm.
That's her sweet spot and probably less than 100 of the 315 horses supposedly available at full noise.
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Old 09-28-2017, 02:19 PM   #47
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I can't reconcile why JD says my boat engine shouldn't idle longer than five minutes without load while observing railroad locomotives and trucks idling for hours on end.
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Old 09-28-2017, 02:45 PM   #48
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I can't reconcile why JD says my boat engine shouldn't idle longer than five minutes without load while observing railroad locomotives and trucks idling for hours on end.
Exactly.
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Old 09-28-2017, 07:41 PM   #49
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I can't reconcile why JD says my boat engine shouldn't idle longer than five minutes without load while observing railroad locomotives and trucks idling for hours on end.
Damn good question!
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Old 09-28-2017, 07:52 PM   #50
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My first 1/2 of my boating life was in sail. There, engines don't last at all well. That is primarily due to so many startups being for just long enough to get out of the marina and get the sails up. No chance of getting the temperature up. I know of many sail boats being re-powered. I only know of few power boats being re-powered. It is not a coincidence.
I did that today with my sailboat. I had to move it from my slip to the guest dock because I can't get out of the slip at low tide. The broker is taking it for a sea trial and survey tomorrow morning. So I started it up, idled in an out of gear for about 20 minutes. Had to back the boat into a tricky spot to tie up. Fortunately, there were some YC members there who were able to take a bow line as the wind was blowing the bow away from the dock.

The engine never really made it to temp and I was going in and out of gear a LOT to get the boat to back in the right direction. It has been too long since I have done that with the sailboat. At this point, it would have been easier with my NP43 with its bow and stern thrusters.
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Old 09-28-2017, 07:57 PM   #51
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I did that today with my sailboat. I had to move it from my slip to the guest dock because I can't get out of the slip at low tide. The broker is taking it for a sea trial and survey tomorrow morning. So I started it up, idled in an out of gear for about 20 minutes. Had to back the boat into a tricky spot to tie up. Fortunately, there were some YC members there who were able to take a bow line as the wind was blowing the bow away from the dock.

The engine never really made it to temp and I was going in and out of gear a LOT to get the boat to back in the right direction. It has been too long since I have done that with the sailboat. At this point, it would have been easier with my NP43 with its bow and stern thrusters.
Wifey B: After coming over to our side, you just can't go back.

It does bring up an interesting question. We know lots of powerboaters had sailboats first. I wonder how many the other way around. I would think far smaller percentage who have gone from power to sail.
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Old 09-28-2017, 09:19 PM   #52
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I can't reconcile why JD says my boat engine shouldn't idle longer than five minutes without load while observing railroad locomotives and trucks idling for hours on end.
Its because they soon will be properly loaded which raises exhaust temps to clear the carbon buildup from idling. Now if those same locomotives and trucks were NEVER or rarely loaded, then you would have carbon caused problems at the very least. Those idling engines as I recall seem to smoke more than most boats. Is it from zillions of run hours or cyl glazing. Who knows? For the most part we're all just guessing.
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Old 09-28-2017, 11:39 PM   #53
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Wifey B: After coming over to our side, you just can't go back.

It does bring up an interesting question. We know lots of powerboaters had sailboats first. I wonder how many the other way around. I would think far smaller percentage who have gone from power to sail.
Well... You might see a few more in their early years rather than say "over 50" to go from power to sailing. Sailing contains a rather romantic history don't cha know!

For the after 50 group... sailing to power is I believe the main stream for "pleasure" boating.
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Old 09-29-2017, 02:48 AM   #54
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Railroad engines are not unloaded, they are diesel-electric and there is always a load on them. Fish osts run to the fishing grounds, are fully up to temperature and then are at low load for long periods, NOT idling.
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Old 09-29-2017, 03:07 AM   #55
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Railroad engines are not unloaded, they are diesel-electric and there is always a load on them. Fish osts run to the fishing grounds, are fully up to temperature and then are at low load for long periods, NOT idling.
Regardless, my JD powers an alternator so there is some load even if the propeller shaft isn't turning. How's that different than a locomotive producing some electricity too? ... On the other hand, I can see a difference from idling a cold engine as opposed to a fully-heated engine.
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Old 09-29-2017, 09:04 AM   #56
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As for idling....

We really need to get the engine up to temp to burn off carbon and water deposits. And that can easily be done in the 40% of power range.

But what probably would be harmful, if one idled the boat for a long time, perhaps to charge up a battery, and then shut down and never got up to temp. Then you still have all that crap in the engine.
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Old 09-29-2017, 09:12 AM   #57
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Had a strange thing happen last night.

Started the boat, like I have many times before, and often let it idle for a bit. This time went back into the house to help the Admiral get ready and that took an hour.... she couldn't decide what to wear.

When I got back to the boat, the engine had quit. I had all the electronics on, so I started the genny to add a little charge to the battery and a bit later started the engine. Ran fine. Nothing seemed wrong.

Ran it for a short run, about 15 min. Shut down for a few hours, started up again for another 15 min run and everything was fine.

Just wondering what caused it to quit.

Usually it's a fuel problem, but apparently not, as it ran fine again and the genny ran without a hitch. Spec of water? Don't know.

Thoughts?
What model motor? Specifically, what happens when you shut down the motor? Does a solenoid turn on, turn off, or mechanical fuel off or ??
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Old 09-29-2017, 10:38 AM   #58
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What model motor? Specifically, what happens when you shut down the motor? Does a solenoid turn on, turn off, or mechanical fuel off or ??
Diver Dave,

It's a Yanmar 6LYA STP, 370 hp., electronic controls. There's a magnetic switch on the starter that starts it when the switch is closed. The engine is stopped wit a solenoid that turns off fuel flow when the stop switch is closed.
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Old 09-29-2017, 11:41 AM   #59
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Diver Dave,

The engine is stopped wit a solenoid that turns off fuel flow when the stop switch is closed.
This engine does have an "emergency stop" button, different from the normal "engine stop" control.

Of course, being an electronic engine, it will have diagnostic codes that are readable over the CAN bus. I'm looking at the ECS manual now, and it may log the "emergency stop" command. Not sure if it is "sticky" though.

I suppose where I am going with this is it may be worth checking some easy stuff, since you don't want "uncommanded stops" when underway. A number of connections and electronic sensors need to work the keep this engine spinning.
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Old 09-29-2017, 11:49 AM   #60
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This engine does have an "emergency stop" button, different from the normal "engine stop" control.

Of course, being an electronic engine, it will have diagnostic codes that are readable over the CAN bus. I'm looking at the ECS manual now, and it may log the "emergency stop" command. Not sure if it is "sticky" though.

I suppose where I am going with this is it may be worth checking some easy stuff, since you don't want "uncommanded stops" when underway. A number of connections and electronic sensors need to work the keep this engine spinning.
Thanks Diver Dave,

I've had the "auto stop" stuff fail engines on other boats but not diesels. The only emergency stop that I know of is if the fire extinguisher is activated. At least there's no manual one. Will look at the manual again on that one.
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