Going Nuts

Posted: March 1, 2014  |  Tag: 

By: John Temple

I have an age-old question. I have a 1990 33-foot Sea Ray with twin 5.7L inboards and v-drives (a very common inboard setup among many boat manufacturers). When installing the props on the shafts, there are two nuts, one thin and one thick. Which nut goes on first? I have walked around our yard and seen them on both ways, so which is the correct way? The most popular way seems to be the thick one first. Is there a logic for installing them any particular way?
Generally, the thick one goes on first. This is the one that locks the prop into place, and since it has more threads than the thin one, it puts more pressure on the prop than the thin one would. The thin one is, in effect, a lock nut — not a great one, but it does work. Many boaters purchase a proper lock nut of the appropriate size if they can get one. Other boaters use a lock-tight material in the threads of the thin one before they put it on. Since the thin nut is so thin, a good wrench will break it free of the seizing material if it ever needs to be removed.

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