For what it's worth, I had a very old oil pressure sender on a Westerbeke 4-107 fail once on me in such a way that the alarm didn't sound but 5 qts of oil squirted out into the bilge on a trip from the CCC to Gloucester. The oil pressure alarm sounded just as we picked up a mooring in Gloucester. Beware of old oil pressure senders, especially if you should see any oil dripping. At 40 psi it doesn't take too long to pump out 5 qts.