Yanmar 150 HP break-in process

[baz]

I read following in Operation Manual

-During the first 50 hours of operation, operate your new engine under a substantial load at all times. For best break-in results, operate the engine at various speeds.

-Operating the engine in NEUTRAL must be avoided. During the first 50 hours, avoid operation below 2000 rpm.

I find the above to be counter intuitive. Normally, one goes easy with a new engine.

"Substantial load" means what ?

How can one avoid operating engine in NEUTRAL ?

Running the boat in and in the vicinity of my Marina the engine rpms have to be below 2000 to keep speed down!

 

[Levitation]

No NEUTRAL means do not have the engine in neutral, then run the throttle up to cruise RPM, and go out for a 5 course lunch...
The reason is, that breaking-in the rings to fit the cylinder requires significant cylinder gas pressure to get behind the ring and push it out against the cylinder wall... An engine spinning with no load does not generate enough cylinder gas pressure and the rings are not thrust against the cylinder walls with enough pressure to hone them to a fit.. Running like this for extended periods will end up glazing the cylinder wall (hot gas blow by) and require a hone job and fresh rings to start over on the break-in process (mucho $$)... Just starting the engine in neutral while you undo lines, etc. and idling out of the marina, will not harm the engine...

And loading the engine, means don't baby it by ghosting along at idle for the first 20 hours.. Go out and cruise... And when you can, run full throttle for 60 seconds every 15 to 20 minutes..
And lastly, don't get all tense over this... Cruise the boat and the engine will break-in just fine...

 

[bbrh842]

Owner manual for my 110 HP yanmar says:

During fist 50 hours avoid operating at low rpms or light loads for more than 30 minutes at a time.

First 10 hours operate at 60% to 70% load as much as possible.
Do not operate at wide open throttle for more than one minute.

After 10 hours, during each 30 minute period, 70% power for 15 minutes, 80% power for 10 minutes, 100% power for 5 minutes.