Originally Posted by BubbleheadMd
The "taste test" is inconclusive.
Rainwater running into an engine bilge where the stuffing box drains to, will taste salty.
The "powder test" is much more effective. Buy a cheap rose bush duster from the hardware store, and load it with DE powder (diatomaceous earth, also at the hardware store).
DE powder is very fine, harmless and cheap. Give some puffs of that around your bilges and watch the water trails illuminate like magic.
And it will kill any insects that happen to come on board!