Jay,
Since we are speaking of first party coverages, you have to refer back to the policy to determine coverage. Some policies are all risk, except for named exclusions. So, yes you can be negligent in your maintenance and collect. You don't have coverage for the cause of the loss, but do for the resulting damages. Example: you need a new roof and don't replace it, water leaks in and damages structure and contents, the structure would be covered except for the (roof), but contents aren't covered. As to the boat you would need to read the policy as to causes of loss. Yes, if it were to snap off below deck with no knowledge, you would need to see what the cause of loss requirements are in the policy but other resulting damages would be covered, neither the item or cost to repair it is.