Re: Mfg oil vs Synthetic for breaking in
I worked for an accredited laboratory that tested and certified outboard oils.
When any NMMA TC-W3 candidate outboard oil is tested and certified (using standardized tests in actual outboard engines), that oil is also used for break-in on the new test engine powerhead. This includes any candidate synthetic oils.
The synthetic oil either passes or fails the certification process, which includes evaluating and measuring piston skirt varnish, undercrown deposits, crownland deposits, second land deposits, ring sticking, compression, etc.
Break-in is part of that test. Break-in on the candidate oil is approximately a short 2 to 2-1/2 hours. At that point the engine is considered ready to perform the endurance testing and other tests.
Obviously a synthetic oil can not become NMMA TC-W3 certified if it can not be used as the break-in oil. In my years of experience, I do not recall a candidate synthetic or semi-synthetic 2-stroke outboard oil that could not be used as the break-in oil (ie: a failed test because of inadequate break-in).
Synthetic 2-stroke outboard oils are not so "slippery" as to not allow proper break-in. In fact, some non-synthetic candidate 2-stroke oils showed less wear after break-in.
I admire Bwalker for sticking to his guns on this. There is a lot of misinformation out there that conflicts with actual results. How the engine is "broken-in" (RPM, load, time, cooling, fuel, etc.) are much more important than the oil used. In my experience, I see no problem in using a synthetic oil for breaking-in an outboard, at least until the manufacturers say you shouldn't.