Long Idle Conditions (hours) – What effects/ recommendations

[crhodes]

Diesel Dudes,

Seriously considering diesel as a repower option however one strong barrier may be long periods (up to 4 hours) of slow trolling at idle conditions. My experience with large commercial diesels is that they should not be operated for long periods at idle. Have no idea if this applies to today’s newer, higher rpm diesels.

Two questions: 1) What is your diesel manufacturer’s position on this issue. 2) What experience if any do you have with idling your diesel for hours?

Please identify the diesel you are running.

Thanks in advance for your response.

[Pedlyr]

My shamrock has a gas engine, but I work with larger diesels on boats every day. Mostly newer Caterpillar and Cummins with computers.

Now, with stringent EPA diesel emmission requirements, even larger diesels must burn cleaner as well as the smaller ones. This is usually achieved with high injection pressures that computers can control and monitor.

The Cummins QSK series (not the 6BT), most CATS and I think the Volvo's do this. I'm not sure about Yanmars. Basically you don't have a "jerk" style pump where the fuel is controlled and meterd at the pump itself and then sent out to the individual cylinders VIA a fuel line. Instead, you have a "common rail" or a manifold full of fuel that all the injectors tie in to and take only the fuel that they need. Or what the computer lets them.

All this allows for a more complete combustion. Especially at low RPM's where most pollution occurs, which is basically unburned fuel.

As long as you have some sort of a load on most any diesel, I would think you should be fine regardless of RPM's. Idling at the dock out of gear for long periods where the unburned fuel can "wash" the cylinder walls is when you might have a problem. Especially with an older fuel injection system.

Be prepared for "sticker shock". // Ed

[Aqua Vista]

I have never had any issues with my engine idling/trolling slowly for several hours while searching in vain for fish.

[crhodes]

Thanks Pedlyr,

Good education/history lesson.

Was aware sticker shock will be significant. Guessing at least double the cost of a gasoline repower. At best it will likely take 10-15 years to break even on the fuel savings. (Thanks for the warning.)

[fisherofmen]

Cecil.
I have had this conversation with Yanmar on several occassions and I get the same answer. You can troll as long as you want off shore but the key is not to troll for many hours and shut it off without a period of time at cruise throttle. Mastry said the danger is if you have to idle for an hour or more to get back to port and shut if off without getting it up to temp. Apparently which is also obvious, if you don't get above idle you don't get to normal operating temperature which cause the build up of deposits which would normally not accumulate if you run at temp. The key is how long you have been at idle or troll prior to shutting the engine off.

Rick Smith

[ku2c]

Rick, that also matches what Mack Boring told me about the Yanmar's. Suggested 5-10 minutes of cruise for every hour or so of idle trolling.

Pete

[crhodes]

Thanks folks. You are making me feel better!

[Anonymous]

Hey guys ,
I've been trolling for 3 to 4 hrs at a time . Then we go to some speed at about 3000 rpms and everything is ok Usaully on the way home.

Temp at trolling is 160. At running speeds 140 to 160

Len