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Stern gear aft bush / bearing


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Good evening all

 

A very basic question which I can't find the answer to!

 

I have a steel tube (boss) sticking out of the back of my hull. I understand that the inside is threaded to accept a bronze bush, and through the centre of this bush passes my 2" dia prop shaft. (threads visible on the attached example photo).

 

1969341576_rearpropshaftbushmounting.jpg.22448c6add7d8c526b71f4084906e8fd.jpg

 

I have found the steel boss available at Midland Chandlers and it too has threads on the inside so I  assume that the bronze bush is screwed into place from the outside.

 

Please, does anyone have a link to or a photo of these bronze bushes with the appropriate screw threads on the outside surface?

 

Much obliged

 

 

 

 

 

 

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25 minutes ago, dpaws said:

Good evening all

 

A very basic question which I can't find the answer to!

 

I have a steel tube (boss) sticking out of the back of my hull. I understand that the inside is threaded to accept a bronze bush, and through the centre of this bush passes my 2" dia prop shaft. (threads visible on the attached example photo).

 

1969341576_rearpropshaftbushmounting.jpg.22448c6add7d8c526b71f4084906e8fd.jpg

 

I have found the steel boss available at Midland Chandlers and it too has threads on the inside so I  assume that the bronze bush is screwed into place from the outside.

 

Please, does anyone have a link to or a photo of these bronze bushes with the appropriate screw threads on the outside surface?

 

Much obliged

 

 

 

 

 

 

Your bras sterntube screws into it from the inside. The inside of that tube is the bearing for the shaft.

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Oh hell - I knew that I didn't quite have my head around this! So, there's a brass tube that fits inside the steel boss tube with screw threads that it locates on. OK, so what lies between the walls of this brass tube and my spinning prop shaft - and what supports the other end of the brass stern tube in relation to the outer steel boss tube? I think the word bearing is confusing me, because in my head a bearing has balls in it!

Just now, PaulJ said:

Here you go-the whole assembly-the grease cup wouldnt be normal though-this would be replaced with the pipe fitting for your greaser.

2019-10-02 23.42.25.png

Ahhhh.... OK, thanks Paul - so the steel tube on the end is the same steel tube that's welded to my hull

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2 minutes ago, dpaws said:

Oh hell - I knew that I didn't quite have my head around this! So, there's a brass tube that fits inside the steel boss tube with screw threads that it locates on. OK, so what lies between the walls of this brass tube and my spinning prop shaft - and what supports the other end of the brass stern tube in relation to the outer steel boss tube? I think the word bearing is confusing me, because in my head a bearing has balls in it!

No balls, its whats called a plain bearing. You will need a bracket welding in on the inside  of the boat to bolt the inner end of the sterntube to, at the circular flange as in PaulJ's pic.

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3 minutes ago, PaulJ said:

The bearing is threaded either end. One end goes into your steel welded in boss.

Other end has the flange /packing asssembly screwed onto it which in turn is bolted to a steel supporting plate which is normally welded to your hull.

Bingo! I found some brass tubes that were threaded at both ends on the chandlery site - the penny's dropped! Bless - thank you!!!

 

So, when there's movement of the prop itself it's because the inner bore of this brass tube has become worn, so you replace the tube.

 

Thank you guys!!

Edited by dpaws
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23 hours ago, bizzard said:

No balls, its whats called a plain bearing. You will need a bracket welding in on the inside  of the boat to bolt the inner end of the sterntube to, at the circular flange as in PaulJ's pic.

I suspect that the welding marks you can see forward of the boss is the bracket in question.

To the OP. I can understand your confusion. I replaced the sterntube and shaft in my  NB last week and before I did so i always imagined the sterntube was considerably longer than the 7.5 inches it turned out to be (no titters please) It was only when I got all the components in my hands that all became apparant.

1 hour ago, sharpness said:

PS. Where's the skeg?

I imagine that will be added when they lift the hull.

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