Nuts (Two vs One)

Have been following the prop/shaft nutting discussions on which of the usual two nuts goes on first in Passagemaker and Professional Boatbuilder with interest.

Because my powerboat just had a line cutter installed on its short length of exposed shaft, there is now not enough room forward of the prop to install a shaft zinc.

So a zinc prop nut as shown in the attached picture was installed.

There is now not enough room on the threaded end of the shaft for both this new zinc nut and a jam nut and still have the shaft's cotter pin hole exposed enough in one of the slots on the zinc nut to insert the pin, so our local boat yard put the thick bronze washer in the pic between the prop and the zinc nut, tightened it up, put in the cotter pin and called it a day.

I saw one other boat at the yard with this arrangement and the local prop reconditioning shop says this setup is not uncommon when using the zinc nut.

Makes me nervous though not having two nuts (pun intended).

Do anyone have any comments about or experience with this one nut with washer setup?

David,
No experience but I don't want to see this one move off the map. My first thoughts are 1. is a line cutter needed enough to justify changing the original prop set up and 2. is the yard willing to stand behind the repair.
If the yard says "no way" then I would consider it a "questionable install" and consider letting the line cutter go.

We have that exact zinc and the cone that the zinc attaches to is the lock nut and is pinned with a cotter pin through the cone. There is no way the prop nut is coming loose. Chuck

I put a line cutter on my prop shaft with very little clearance and added the prop nut zinc as you showed below. However, the "cage nut" (for lack of a better term) is a nut, and the thin nut is in front of it as a jam nut. No washer. Also has the cotter pin. Totally comfortable with it.

Capn Chuck wrote:

We have that exact zinc and the cone that the zinc attaches to is the lock nut and is pinned with a cotter pin through the cone. There is no way the prop nut is coming loose. Chuck

Click to expand...

Hmm. Thought this thread was going to disappear. Thanks for the replies.

Capn Chuck: Do you have a second (jam) nut in addition to the cone nut? Or just the cone nut with or without the* washer?

Forklift: Yes, the line cutter is absolutely necessary up here in the land of a million lobster buoys and cold water. My "in house" diver (read:the Admiral) has gone over the side with a knife in her teeth several times in the past 22 yrs with our last boat to cut a buoy loose. A line cutter seemed like a good idea on the new boat (especially when I discussed with my diver about whether we should go from two nuts down to one in order to install a line cutter or stay with two nuts and no line cutter, I could hear her cranial gears putting a knife back into the equation).

Would the yard stand behind it? Probably not, as it was our choice to change things around and they are just trying to accommodate us.

*

Keith wrote:

I put a line cutter on my prop shaft with very little clearance and added the prop nut zinc as you showed below. However, the "cage nut" (for lack of a better term) is a nut, and the thin nut is in front of it as a jam nut. No washer. Also has the cotter pin. Totally comfortable with it.

Click to expand...

Posted my reply to Capn Chuck and Forklift before I saw yours. Unfortunately,the use of both the thin (jam) nut plus the "cage nut" extends the combined thickness of the nuts back behind, and thus covers, the cotter pin hole. I suppose I could have the thickness of the jam nut machined down in increments until there is enough clearance for the cotter pin.

David, Ours has the prop, then a single nut, then the cone for the zinc and that is it. Ours does not have a washer, the cone fits right against the prop nut as the second nut usually does. The cotter pin then goes through the slots in the cone and there seems to be plenty of room for the cone to tighten down and get the cotter pin hole lined up. Here is the best photo I have of ours, http://tinyurl.com/l6t5qk , Chuck

-- Edited by Capn Chuck on Tuesday 30th of March 2010 07:50:57 AM

Capn Chuck wrote:

David, Ours has the prop, then a single nut, then the cone for the zinc and that is it. Ours does not have a washer, the cone fits right against the prop nut as the second nut usually does. The cotter pin then goes through the slots in the cone and there seems to be plenty of room for the cone to tighten down and get the cotter pin hole lined up. Here is the best photo I have of ours, http://tinyurl.com/l6t5qk , Chuck

-- Edited by Capn Chuck on Tuesday 30th of March 2010 07:50:57 AM

Click to expand...

Thanks. I think that I may have the small jam nut machined down so that we will have room for both a jam (prop?) nut and the cone nut.

*

Why not drill the second nut so the cotter pin can pass tru

I don't know if this is going to be helpful but we have a single cap nut behind the prop on the end of the shaft with a cotter pin through it.

No washer, no thin nut, no zinc, nothing else at all. Shaft size is 2.75 in. It's all stayed together for 30 years so far....

The taper should hold the prop firmly on the shaft, not the key or the nut. There's a good article by Tony Athens on boatdiesel.com about this very issue.

Jeff b

Bendit wrote:

I don't know if this is going to be helpful but we have a single cap nut behind the prop on the end of the shaft with a cotter pin through it.

No washer, no thin nut, no zinc, nothing else at all. Shaft size is 2.75 in. It's all stayed together for 30 years so far....

The taper should hold the prop firmly on the shaft, not the key or the nut. There's a good article by Tony Athens on boatdiesel.com about this very issue.

Jeff b

Click to expand...

Thanks. Am a member of boatdiesel. Can you point me to the article/thread on the site?

*

Hi David,

The article is at:
http://boatdiesel.com/Articles/Articles.cfm?P=20030201_Prop_Installation.cfm&Y=2003

but having read it again it may not be that helpful. I can only reiterate that one nut with a cotter pin has worked well for me.

David Pascoe had something about this on yachtsurvey.com, but after a quick look, I can't find it. He may have deleted it.

Cheers,

-- Edited by Bendit on Wednesday 31st of March 2010 02:21:01 PM