Doug – couple of thoughts. Nick is correct that the seals do harden and deteriorate over time and putting new ones in makes sound sense. No use in putting replacements in if they’re the same vintage……………………
I had problems nipping up bolts on T4, until I realised that I was backing off the nuts so that the bolt disappeared outboard too far, such that the lug no longer engaged on the head of the bolt. And unless that lug is engaged, it’s virtually impossible to nip the nut up tight enough to stop water leaking in.
Only other suggestion is that if possible, could you beach the boat and let her dry out for three hours or so whilst you whip off the bold head cover plates to check if the lug is engaged on the flat of the bolt head?
Also, just a little nervous if you are relying on a float bilge pump to get rid of the water. These pumps have been known to fail. Also, batteries do flatten with excessive use.
Cheers, Mike