To add an InfoWindow to each marker with JavaScript Google Maps API v3, we set the info property of the marker.

For instance, we write

const marker = new google.maps.Marker({
  map,
  position: point,
  clickable: true,
});

marker.info = new google.maps.InfoWindow({
  content: `<b>Speed:</b>: ${values.inst} knots`,
});

google.maps.event.addListener(marker, "click", () => {
  marker.info.open(map, marker);
});

to create a marker with the Marker constructor.

Then we set its info property to an InfoWindow instance which has the content set to some text.

And then we add a marker click listener with addListener to open the info window with marker.info.open when we click on the marker.