Here are the mistakes in using radar.

Mounting the radar too high.  Ten feet should be enough for a 2 kilowatt set and 15 should be enough for a 4 kw set. These are the sizes of radars on most pleasure craft under 65 feet.

Using a range that does not fit the problem. In other words,
big ships will show at 6 to 8 miles
vessels of about 100 feet at 5
boats 40-60 at about 4 miles and
20-35 at about 3 miles.
(You can improve on this a little, with a 6 or 8 kilowatt radar, but not a lot. At 12 kw, you can pick up the radar radome on a fishing boat at 10 miles).

There is very little use in using a range of more than 6 or 8 miles in any case. And if you want to pick up small vessels, as you can see you need a scale of 3 miles or maybe even less. What most people don't know is that the longer range you use, the longer the radar pulse that is used and the fewer pulses that are sent out. 6 or 8 miles uses a long pulse and since a small boat won't even become visible until less than 3 miles, due to the curvature of the earth and so on, they may actually slip right "under" your radar and you will never see them. It is vital that if you want to pick up smaller vessels that you not go over 3 or 4 miles on your range setting. Frankly I like to set my radar on 3 miles and then offset the screen so that I can see about 4 1/2 miles in front of the boat.

You want to examine the specs for your radar and find out where the set automatically goes to long from medium pulse, generally anything past 3 miles.  Avoid ranges that use long pulses, if you don't want to miss small vessels. If you think you might want to detect kayaks, then you may have to use a mile and a half range.

For instance the Furuno 1731:
2100 pulses per second at .08us in length.   ---- Ranges under 1 1/2 miles.
1200 pulses per second at .3us in length.  ----- Ranges from 1 1/2 miles to 3 miles.
600 pulses per second at  .8us in length.   ------- Ranges over 3 miles.

Notice that the pulses per second are 3 1/2 to 1 from short to long and 2 to 1 from medium to long.
But the pulse lengths are about 10 to one from short to long and about 3 to 1 from medium to long.

In other words, at short ranges the pulses are fast and very short.
At medium the pulses are about twice as fast but about 1/3 as long.
At long ranges the pulses are half as many and about 1/3 as long as at the medium ranges.

Think of yourself as Spock, sitting at his sensor console, tweaking the pulse rate and length to find a cloaked Klingon warship.