I got down to my brothers and found he had moved it so the motor was under a flowering shrub/tree that was losing it’s flowers dropping all over the motor and they were breaking down and were now a similar colour to the stain. There had also been a lot rain down his way.
I inspected (without taking cover off) the Mount cover on both sides. The starboard side was clean as a whistle but the port side looked like this (see picture).
Image1620940302.117314.jpg
The Mount covers appear to have a rubber gasket or similar and they look in good order. The bolts holding cover on all appear fine and no discolouration or rust.
The marks came off very easy using a little bit of polish.
So I’ve taken boat home and will monitor any further stains that may appear.
Shakey - If only I lived near the coast