Gary,
I don't know why I didn't think of the flex line before. When we first had the boat the dealer couldn't figure out the cause of the vibration so the manufacturer flew someone from Florida to our house in CA after I complained to the CEO. When the guy left, everything seemed much quieter, but I didn't realize it was because he'd merely put in a larger accumulator tank. When the pumps kick in they're as noisy as ever.