4.
2 along the keel and 1 either side to keep it upright. I’ve done it a few times.
You might need to tie the boat to something and drive the trailer out from under it to get it off a bunk trailer.
Getting it back on you unhitch the trailer and winch it under the boat. You will need to make sure the trailer won’t take off when the boat reaches the point of balance.
The winch will end up high in the air as the trailer goes under the bow so you may need a small ladder too.
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