It was a flat bottom boat engine with water injected into the exhausts to act as rudimentary silencers. Some salt water spray inevitably found its way into the head and ports and cylinders.
Even with fresh water flushes and oil dribbled into the intake for a few seconds before shut down, a bit of salt stays there and a fine film of rust develops on he bores and valve stems.
Less likely, but of more concern is if it develops as pits or develops on the cam lobes, followers and valve springs.
I turn them over gently. If they feel tight I squirt some keroine/ATF mix down the plug holes and inlet system then rock the crank back and forth to wear the rust off. Provided it's only a light surface dusting of rust it cleans up quite good.
After it frees up I start it if possible, change oil and start it again.
I also, normally use Mobil 1 as I find it leaves a very fine protective coating for longer than mineral oil.
I know that is far from ideal, but sometimes circumstances dictate.
Once the damage is done, there is nothing to lose, as it either runs OK and your in front or scores a bore or pulls a ring land or knocks or loses a lobe or bends a push rod and your no further behind. It needs a freshen up anyway.
Sometimes a ring sticks for a while, but they normally free up then seal up with a few minutes running.
Sometimes a valve spring breaks. That is the worst as it might drop a valve.
Regards
Pat
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