Fair bet it will be electrolysis - most corroded metal on a boat
is, can't think of any time it isn't. As to the survey
, a lot can change in 3 years.
I reckon a corroded bolt on the raw water
strainer will be the least of your problems.
Please don't take offence, but do you have any idea of the potential problems that might follow from a sinking?
If you do, then fair enough, go adhead with your eyes open; however, if you don't, I would advise you to tread carefully until you are more informed.