Bow thruster shear pins - what metal

[Talulah]

Does anyone know what the metal used is in Bow Thruster shear pins?
Tempted to make my own.
Many thanks.

 

[Norman_E]

My Vetus bowthruster shear pin was made of brass. When it sucked in a piece of rope and sheared the pin I made my own replacement from 3mm diameter brass rod. That was for a 55KGf thruster. Bigger ones might have a larger diameter pin.

 

[Talulah]

My Vetus bowthruster shear pin was made of brass. When it sucked in a piece of rope and sheared the pin I made my own replacement from 3mm diameter brass rod. That was for a 55KGf thruster. Bigger ones might have a larger diameter pin.

Many thanks. I know mine are 5mm x 27mm. I can always try brass and see what happens.

 

[Norman_E]

Many thanks. I know mine are 5mm x 27mm. I can always try brass and see what happens.

That should be safe. If you have the bits of the old one, attack one with a file to remove any dirt or plating. If they are yellow metal it will almost certainly be brass. Steel would be unusual for such a use as even mild steel would probably be too strong in shear. It is better for the pin to shear than the prop or motor get damaged, that is what its there for. It must be a big thruster if there is a 5mm pin in the motor shaft, as on the Vetus; or is your pin on the propeller shaft?

 

[SamSalter]

I have to ask:
How expensive can a 5 mm shear pin possibly be?

 

[VicS]

I have to ask:
How expensive can a 5 mm shear pin possibly be?

Vetus stuff is extremely expensive
Those pins are anything between about £3 a just over £5 each depending upon which model of thruster they are for.

A big dent in the annual budget perhaps. Enough to buy 3 or 3 litre of diesel!

 

[Talulah]

I have to ask:
How expensive can a 5 mm shear pin possibly be?

£4.95 + postage

1m of 5mm brass rod can bought on ebay for £6 inc postage making them 35p each.

 

[Talulah]

That should be safe. If you have the bits of the old one, attack one with a file to remove any dirt or plating. If they are yellow metal it will almost certainly be brass. Steel would be unusual for such a use as even mild steel would probably be too strong in shear. It is better for the pin to shear than the prop or motor get damaged, that is what its there for. It must be a big thruster if there is a 5mm pin in the motor shaft, as on the Vetus; or is your pin on the propeller shaft?

The Sleipner thrusters use to have the shear pin on the motor shaft.
We have an SE80 thruster. The shear pin is longer on the motor shaft but on the prop shafts just behind the props instead. Where there used to be a shear pin on the motor shaft there is now a Woodruff key.
This is a curse. With the old Sleipner thruster you could change the shear pin with the boat in the water. With the new Sidepower thruster you have to have the boat out of the water to change the shear pins.
Incidentally, a friend of ours did not tighten the anode bolt up enough. When it fell off in use it destroyed his thruster props. (Replacements props are about £50 each.)