Hi, vermae. Welcome to DC.
I've been cooking for about 50 years and have cooked my share of potatoes. I have a rice steamer that has a vegetable steamer insert. That's what I've been using recently to cook potatoes for potato salad. I set the steamer ON and gauge the doneness of the potatoes by inserting a thin-bladed knife into one. If the knife slips in with little resistance, the potatoes are done. Using the steamer keeps the potatoes out of water so they're nice and dry for potato salad.
Actually, when I cooked my potatoes in boiling water, I used the same knife test. I made sure to remove the potatoes from the hot water immediately to a strainer or colander so they could cool and have any residual water drain away. There will be some carry-over cooking because they are so hot.
Hope my answer helps.
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