Hi Mike,
I understand. It is not easy and requires strength. You can't "step" the mast on the Sidewinder because you can't hook up the shrouds beforehand, pin the base of the mast in place and then walk (or step) it upright like you can on other boats. The only solution is to hold it upright and insert it into the hole. The shrouds have to be hooked up after the mast is in place.
The only way I would personally attempt it in the water were if the boat were on a sandy shore and you could get a firm footing on the ground. I can't imagine holding this huge heavy pole upright while standing in a boat floating in the water!
The first task is to get the mast upright. For that, you could place against an immovable object (such as a large stone or a curb or even a tree) and walk it upright. Then you need to get it to the boat. Move slow, setting the base of the mast on the ground and take frequent breaks if you need to. The hardest part is then lifting it up high enough to clear the boat and getting it into the hole. I have no suggestions for an easy way to do that.
Paul
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