Avoiding Carbon on Engine - MD2B Volvo diesel

[zinahewitt]

Hi All,

Hope your Jan is going well.
I have an MD2B VOLVO penta.
The engine is from the 70s.

I was told that using it to get in and out like I do is bad for it.
So.
I researched and it looks like the recommendation is to run it at high speed for a while.
The so called "Italian Tune Up"

The problem is it is not clear as to what is high speed and what is a while.

I assume
Warm up - Idle 10 minutes.
Get out.
Then what 1/2 ? , 2/3s ? 90% or full speed
for
A period of 5 minutes ? 10 minutes ? 30 minutes ? one person said an hour

or do I motor normally, then just do it for 10 minutes every time

Do you do this once a season ? every time ? whenever possible.


Thank you
Saar

 

[dlochner]

Do you have a Tach? If so find WOT (wide open throttle) by opening the throttle all the way and recording the RPM. The ideal engine speed is 80% of that rpm.

Running the engine for 10 minutes at idle is not the best practice, half that is more than enough. Usually I start the engine and then take my time uniting the boat. Once we are untied I slowly back out and leave accelerating as I leave the marina. It is only necessary to get the oil running through the engine, which only take a few minutes. Running fast more often is better than less often. On the way back to the marina run it fast for a few minutes after each sail.

This article by Steve D'Antoino explains the issue with running diesels at low rpms. Steve is a highly respected marine surveyor and consultant. His primary clients are buying boats in the 7 and 8 figures, but he hasn't forgotten his roots and all of us out here fending for ourselves. Subscribe to his free newsletter and poke around in his past articles.

Editorial: Soliciting Negative Feedback – Feature: Of Piston Rings, Cross Hatch, Blow-By and Carbon | Steve D'Antonio Marine Consulting

 

[jssailem]

You raise a good question. There will be many answers. Many good, some not so much.

My answer is what I do.
My understanding of diesels is based on my engine, a Perkins 4.107, and others I have been around, be it John Deere tractors or small diesels in boats from the 60/70's.
Your Volvo Penta MD2B is a similar 2-cylinder 4-stroke diesel to my 4-cylinder small boat engine.

The MD2B is designed to produce 25hp continuously at 2500rpm. (see attached PDF specs on your engine).

Generally, diesels enjoy running underload. Sitting in the slip at idle is not ideal. They are workhorses, not idlers. The idea of reducing carbon buildup can only be done when the engine is warm.

My first steps are to check the oil and the coolant levels on the engine. I record the engine start hours, fuel levels, and confirm that the fuel tank that has fuel is switched open to the engine. I then turn on the starter battery. I am now ready to untie the lines.

I will start the engine. Affirm that there is water coming out of the exhaust and the oil pressure is normal. I advance the fuel control and note that it is working, the tach is operating, and that the volume of water increases as the engine speeds up from idle to 1200 rpm. I return the engine to idle 850 rpm, I untie the lines, and get back aboard at the helm. The time frame from engine start to leaving the slip is less than 10 minutes. This is enough time to confirm that the engine is running and that when in gear, the prop is producing thrust. Leaving the marina is accomplished at about 1000 rpm. The engine is under load, and it is beginning to warm. I monitor it, looking for the temp to get to 155º F. When I clear the marina, I have about a mile to go downriver. I do this at cruising speed 3200 rpm for me (your engine would be at 2500rpm according to the spec PDF). All told, from engine start until I have the sails up is about 30 minutes. If the wind is not there, then I run the engine at my cruise until I have to slow down or turn off the engine.

Some feel the need to "clear the engine" before shutting down. This is said to be accomplished by running the engine up to wide open throttle (WOT) or cruise rpm's for several minutes before shut-down. I think if you have been running the engine at cruise rpms (80-85% WOT) that the clearing procedure is not needed. If the engine has been babyied at 50% or less rpm's, then maybe when you do it, black smoke (CARBON FOULING) erupts from the exhaust, there is value in the clearing procedure.

Good luck.

 

[Stu Jackson]

Running the engine for 10 minutes at idle is not the best practice, half that is more than enough.

i agree with Dave. Just ONLY puttering at idle is not good for any engine, especially diesels which LIKE to be run, which is what they are made to do.
In my 18 years in San Francisco, from 1998 to 2016, I would ready the boat, and only then start the engine, back out of my slip, putter less than five minutes out the fairway to The Estuary (which is what constituted my "warmup" - not at the slip) and drive 40 minutes to The Bay. Coming back, I'd either sail back down The Estuary or motor those 40 minutes again.
Here in British Columbia there is often more motoring than sailing.
Just run the engine for five minutes or more at cruising speed as Dave defined it and you'll be fine. Just stop ONLY puttering. Good luck & all the best.

 

[Ralph Johnstone]

I start and leave the slip pretty well immediately. Motoring out of the marina is part of the warm up and then 80% thereafter with an occasional 100% for five minutes every couple of hours.

I was told that using it to get in and out like I do is bad for it.

I presume from that statement, you shut down the engine and raise the sails immediately that you are out of the marina ? Your engine never sees any running under load ?

 

[colemj]

The engine is from the 70s.

Pretty much all you need to know. It is still working well under the "non-ideal" usage pattern you describe after 50yrs of this abuse.

All of what has been said is theoretically true. However, in the practical world, the way you use your engine is how most people use their engines, and these engines continue to run just fine. Maybe they need injectors or elbows replaced more often. Maybe they theoretically don't have the same absolute specifications after 50yrs that a "properly" treated engine would. But all of that is splitting hairs if both are operating within specs at 50yrs, and the only difference is the "abused" one needed the injectors serviced and the elbow replaced one more time than the other.

This is just another "perfect vs good" bugaboo that invades sailing discussions. Not as bad as LFP batteries, anchors, and some other things, but still always there. Ask yourself how many young diesels you have heard of that needed complete rebuilds because they were used like you use yours. Ask other people the same. What you will hear is random one-off examples - probably none first hand - and nothing resembling a wide-scale issue or pattern of usage.

Keep in mind that all of the problems discussed from low loaded engines also require time operating at those low loads. Lots of time. Not the accumulated few minutes it takes you to putter past the marine entrance. Pretty much all examples cited are ones where a larger engine is used for hours each day with a small alternator to charge batteries. Even then, none of those experience problems in the first 2-3,000hrs of use.

Of course it is easy to occasionally run the engine to 80% of WOT for 10-20min to increase temps and help burn things off a bit, and that is a good thing to do, but it won't matter much on a 50yr old engine.

Mark

 

[ice breaker]

My 2004 YANMAR 4JH3E manual says to run at full throttle, 3800 rpm, after extended slow speed use. This facilitates cleaning the carbon off the valves, and helps prevent stuck valves. I do a lot of trolling, and after that I do full throttle for 10 minutes. Engine has 1700 hours and no issues. This engine is rated at full throttle 3800 rpm for 1hr, and then 3650 rpm continuously.

You might want to find the service manual for that engine and see what volvo recommends.

 

[jssailem]

You might want to find the service manual for that engine and see what volvo recommends.

Read post #3 and the attached PDF file for that answer.