Babying a diesel engine

[sv Stella Maris]

Too...many...replies...

...dang it, that was one more! 😂

read your manuals people, yeesh!

[Fore and Aft]

Blubaju I am no expert and enjoy hearing other people’s opinions. 2400rpm is our sweet spot but sometimes it’s nice to do 3000rpm for an hour just get to the anchorage a bit quicker. That got me thinking that difference in engine life between flogging our motor and just babying it might not be that much.
Cheers

[BonesD]

I don’t know how relevant this is to modern day engines but running an engine under spec rpms can result in a ridge to form in the cylinder. The rods etc in the power train stretch a bit when running and the problem that can occur is to run the engine up to a higher than common rpm means the rods are stretching a bit more and the rings can hit those ridges causing early failure. This is stuff I learned 45 years ago so take it with a grain of salt.
I agree with some of the others, run the engine to its potential.

[and4ew]

I've got a Yanmar 2GM20 with 900 hours on it. Runs great. My boat also has a radar system that draws a lot of power, so much that my old batteries can't keep up. If I start the engine then of course the radar works fine. I was thinking that if I was under sail and in fog I would simply run the diesel at low RPM (~1,000) to keep the radar going. From what I've read in this thread that may be a bad idea. I'm not expecting to do this very often (I usually wait until the fog burns off) but I do want to understand what impact doing this would have. Are there any alternative suggestions (apart from getting newer, bigger batteries).

[Wotname]

Originally Posted by and4ew

I've got a Yanmar 2GM20 with 900 hours on it. Runs great. My boat also has a radar system that draws a lot of power, so much that my old batteries can't keep up. If I start the engine then of course the radar works fine. I was thinking that if I was under sail and in fog I would simply run the diesel at low RPM (~1,000) to keep the radar going. From what I've read in this thread that may be a bad idea. I'm not expecting to do this very often (I usually wait until the fog burns off) but I do want to understand what impact doing this would have. Are there any alternative suggestions (apart from getting newer, bigger batteries).

Run it gear and a bit higher revs, say 1200 to 1500 to load it up a bit. Follow the Yanmar recommendation and run it over 3000 for ten minutes every two hours and you will be sweet (IMO / IME).

[chrisr]

Originally Posted by Wotname

Run it gear and a bit higher revs, say 1200 to 1500 to load it up a bit. Follow the Yanmar recommendation and run it over 3000 for ten minutes every two hours and you will be sweet (IMO / IME).

i can see a potential problem in that if you need to run the engine so can use the radar in fog, chances are you wish to go rather slowly...and so don't really feel like running engine at high revs (even for short periods)

can't really see an answer to this though...

cheers,

[yr2030]

Originally Posted by and4ew

I've got a Yanmar 2GM20 with 900 hours on it. Runs great. My boat also has a radar system that draws a lot of power, so much that my old batteries can't keep up. If I start the engine then of course the radar works fine. I was thinking that if I was under sail and in fog I would simply run the diesel at low RPM (~1,000) to keep the radar going. From what I've read in this thread that may be a bad idea. I'm not expecting to do this very often (I usually wait until the fog burns off) but I do want to understand what impact doing this would have. Are there any alternative suggestions (apart from getting newer, bigger batteries).

I run my radar off the generator

[a64pilot]

Originally Posted by chrisr

our 40' 7.5mt cruising cat is well over engineed imho. pair of 4JH yanmars @ 55hp ea, where usual in this size would be 30-40hp

this has resulted in me usually running engines at too low rpm (1500 or so) and STUPIDLY not bumping up the revs every so often to heat the engine/s up properly.

result is one engine is blowing some white smoke ie i have (i believe) glazed the cylinders.

now being much more conscious about running at higher rpm and / or boosting rpm for short periods.



but what to do about the existing glaze ? is it true that this can only be fixed by dismantling and honing ?

cheers,

White smoke is not from glazing, it may be fuel, glazing will cause you to burn oil, which of course shows up as oil consumption on the stick, but also it’s blue and stinks, we have all smelt an old car that burns oil. If it doesn’t stink like that, it’s not oil.

Anyway I’d have your injectors cleaned, and if your concerned with glazing a good detergent in the fuel and or oil will often clean it off, sea foam is apparently well thought of.
Severe glazing is actually very rare, especially on a well run in motor and can only be fixed by honing.
I stupidly forgot and left a bulldozer idling for a long weekend and it hurt nothing, it blew smoke and even oil out of the stack for a few minutes but was fine, I mean it actually blew liquid oil and fuel out the stack and onto the hood.
Severe glazing is very rare and almost always occurs on a new motor that is run at very low output for extended time, before the rings have seated.
But if your concerned add the detergent and take it out and give it a good “Italian tune up” go ahead and run the snot out of it, if it’s cooling system is in good shape it won’t hurt, nothing wrong with running one up every now and again, in my opinion it really will help blow one out and does test the cooling system.
You don’t want your cooling system to deteriorate over time until your engine overheats at 1500 RPM, you want to catch that early, and a very good way is to run one hard for 15 min or so ever so often.

Where I disagree with many is the theory that they like to have the snot run out of them continuously, that’s not true for any engine, Diesels will often tolerate it better than a HO gas motor, but that doesn’t mean they “like” it or that it extends life.
De-rated motors will tolerate it best simply because wide open really isn’t wide open.

My belief is to run one up at the end of the day, go ahead and take it slowly up to about its max output, leave it there until temps stabilize, then slowly back it down, idle it for 5 min or so before shutdown, especially if it’s a turbo motor

[a64pilot]

Originally Posted by BonesD

I don’t know how relevant this is to modern day engines but running an engine under spec rpms can result in a ridge to form in the cylinder. The rods etc in the power train stretch a bit when running and the problem that can occur is to run the engine up to a higher than common rpm means the rods are stretching a bit more and the rings can hit those ridges causing early failure. This is stuff I learned 45 years ago so take it with a grain of salt.
I agree with some of the others, run the engine to its potential.

It’s not from running under spec, it’s from running at one set RPM so that the rings stop at exactly the same place always, it’s the supposed reason to not buy the car from the little ole lady that only drove to church on Sundays, and you running it hard, it will supposedly break rings.


It’s generators that often have the longest lives of any Diesel engines, and it’s generators that blow up a lot of myths.
If you believed most myths, generators would never make it to 1,000 hours as they always run at one set RPM that never varies, and most often not at a very high load either, and yet many last a very, very long time.
10,000 hours is not all that uncommon for a generator.

[chrisr]

Originally Posted by a64pilot

White smoke is not from glazing, it may be fuel, glazing will cause you to burn oil, which of course shows up as oil consumption on the stick, but also it’s blue and stinks, we have all smelt an old car that burns oil. If it doesn’t stink like that, it’s not oil.

Anyway I’d have your injectors cleaned, and if your concerned with glazing a good detergent in the fuel and or oil will often clean it off, sea foam is apparently well thought of.
Severe glazing is actually very rare, especially on a well run in motor and can only be fixed by honing.
I stupidly forgot and left a bulldozer idling for a long weekend and it hurt nothing, it blew smoke and even oil out of the stack for a few minutes but was fine, I mean it actually blew liquid oil and fuel out the stack and onto the hood.
Severe glazing is very rare and almost always occurs on a new motor that is run at very low output for extended time, before the rings have seated.
But if your concerned add the detergent and take it out and give it a good “Italian tune up” go ahead and run the snot out of it, if it’s cooling system is in good shape it won’t hurt, nothing wrong with running one up every now and again, in my opinion it really will help blow one out and does test the cooling system.

thanks...good advice. i'll look into this a bit more

cheers,

[yr2030]

Originally Posted by a64pilot

It’s not from running under spec, it’s from running at one set RPM so that the rings stop at exactly the same place always, it’s the supposed reason to not buy the car from the little ole lady that only drove to church on Sundays, and you running it hard, it will supposedly break rings.


It’s generators that often have the longest lives of any Diesel engines, and it’s generators that blow up a lot of myths.
If you believed most myths, generators would never make it to 1,000 hours as they always run at one set RPM that never varies, and most often not at a very high load either, and yet many last a very, very long time.
10,000 hours is not all that uncommon for a generator.

That's because most generators or gensets are naturally aspirated. Mine has close to 14,000 hrs now. I've had them go 20,000 or more.

[a64pilot]

Most smaller sailboat motors are also normally aspirated also and don’t usually come close to those kind of hours

[a64pilot]

Originally Posted by chrisr

thanks...good advice. i'll look into this a bit more

cheers,

Been thinking about you, you may want to consider running only one engine at a time, and running it a little harder, not running the snot out of it but instead of cruising with both turning 1500, only run one but maybe say 2500 or so. Not when docking etc, but just out motoring to a destination etc.
This also would cut the hours you put on your motors in half, now I don’t have a Cat and never have, but the ability to run on only one motor is attractive, and may be one reason why yours are a little on the big side so that the boat can comfortably cruise single engine?