When surveying sail boats - the keel step and keel bolts require close inspection. First - you want to determine if there's any movement at the keep step (perhaps an indication of grounding or fastener problems) - then for sure - you need to examine the keel bolts for serviceability (wastage). Usually, the step is easy to see - but a fair amount of time - the keel bolts are frequently un-accessible - hidden under tankage - gear - or fixtures. Getting a good clear view of these bolts is sometimes a real problem - but you got to try. Here' some great pics on what the keel stub and bolt thing is all about. Usually - stainless steel keel bolts are placed in the casting - can you say hidden alloy breakdown - corrosion?