I was interested in this discussion on another post but did not want to hijack the topic.
It would seem logical as engines have developed over time and tolerances decreased, the 'running in period' should have also decreased.
Have the manufacturies change their instructions over time?
I have followed the instructions running in three motors this year. (two 2 stroke and one 4 stroke). All were 10 hours.
What is the running in period for diesels ?

cisco said..
If you consider a motor vehicle where the manufacturer might specify a running in period of 10,000 klms. At 100 klms/hour this equates to 100 hours of running.
Therefore a running in period of 100 hours for a marine diesel would seem to be appropriate.

I spent around 25 years working in Toyota and various other dealerships I can't remember any actual running in period specified by Toyota or the others but just to drive it as you normally would

I would contact the manufacturer of the engine in question and see what they say

Regards Don

cisco said..
If you consider a motor vehicle where the manufacturer might specify a running in period of 10,000 klms. At 100 klms/hour this equates to 100 hours of running.
Therefore a running in period of 100 hours for a marine diesel would seem to be appropriate.

I would be talking with Kubota about that. Diesel engines love "load".

If you nurse that engine you will surely glaze the bores. This "running in" idea/proceedure is not generally relevant today.

Engine manufacturers have figured it out and no longer make engines to the size tolerances that require a "running in" period. They deliver engines "ready for work".

You are "allowed" to run the engine at whatever load capacity you "choose". Of course running it as the manufacturer recommends is recommended for warranty purposes.

Cisco, I am having a little difficulty reconciling these two statements of your's, which do you think is actually more appropriate here?

From my Yanmar manual:

A new Yanmar diesel engine must be operated at suitable speeds and power settings during the break in period to make the sliding parts, such as piston rings, break in properly and to stabilize engine combustion. During the break-in period, the engine coolant temperature gauge should be monitored, temperature should be between 71? - 87?C (160? - 190?F). During the first 10 hours of operation, the engine should be run at maximum rpm minus 400 - 500 rpm (approximately 60 - 70% of load) most of the time. This will ensure the sliding parts break-in properly. During this period, avoid operating at maximum engine speed and load to avoid damaging or scoring sliding parts. NOTICE: Do not operate at WOT (wide open throttle) for more than a minute at a time during the first 10 hours of operation. Do not operate the engine at low idle or at low speed and light load for more than 30 minutes at a time. Since unburned fuel and engine oil will adhere to the piston rings when operating at low speeds for long periods, this will interfere with proper movement of the rings and the lube oil consumption may increase. Low idle speed does not allow break-in of sliding parts. If operating engine at low speed and light load, you must race the engine to clean the carbon from the cylinders and fuel injection valve.

Perform this procedure in open waters: ? With the clutch in NEUTRAL, accelerate from the low speed position to the high speed position briefly. ? Repeat this process five times. Once past the initial 10 hours until 50 hours, the engine should be used over its full operating range, with special emphasis on running at relatively high power settings. This is not the time for an extended cruise at idle or low speed. The boat should be run at maximum speed minus 400 rpm most of the time (approximately 70% load), with a 10 minute run at maximum minus 200 rpm (approximately 80% load) every 30 minutes and a 4-5 minute period of operation at WOT (wide open throttle) once each 30 minutes. During this period, be sure not to operate your engine at low speed and light load for more than 30 minutes. If operating engine at low speed and light load by necessity, just after the low idle operation, be sure to race the engine.


Even now, every time before shutting down, I always give it 5 full range revs in neutral to burn off carbon from the cylinders and injectors.

cisco said..

UncleBob said..
Cisco, I am having a little difficulty reconciling these two statements of your's, which do you think is actually more appropriate here?

Which two statements? I made seven.

Ah, mabee the two quoted.

Ok Bob, you win.
Hey oldboy, two thousand hours is 10,000 miles in a yacht at 5 knots. Near circumnavigate the Island of Oz with that!!
I reckon your and samstudy's engines will out live most of us in this room.

I agree newer engines are not so critical, but I still do it.
My running in of the Volvo Penta was drive it normally, ie: just use it for its intended purpose with no aberrations such as excessively long periods in idle or flat out etc.
Its pretty much common sense Sam, don't run it for 50 hours on the dock in idle, nor do you want to run it flat out for the same period. Just let the engine experience its normal working loads without any excessive extreme periods.

The only real critical part for my run in phase was to religiously adhere to the first service (50 hours) and that is mainly for the oil change. It's a new engine, you want an engine oil flush/filters to get rid of any contaminants, and the first service is that chance.

Advice is sourced from a few diesel mechanics, I'm surrounded by them!
Cheers mate,
SB