It seems that many bolts on my Seagulls do not have them. For example, only flat washers on the head bolts and the 4 crankcase bolts. My oldest motor had lockwashers on the two bolts that hold the block on, but neither other motor has them.
To me it seems it would be better to have them in all cases, than not, but then again, that may be Matt Logic, not reality

Oh, and another thing that catches my eye - is my entire EFPC motor staying out of the water by relying on a plastic collar around the shaft where it pivots?? I noticed that the older ones are made of metal, but even that still seems like a single point of potential kersplash. Is there a history of these failing, in particular the plastic bit on a long shaft (which puts more of a moment, hence strain on it)?