Weird size prop nuts for 2 inch shaft. GB 42C

[FBoykin]

My 2000 GB42 has an uncommon thread size and standard 2" shaft prop nuts don't fit. Common available size is 1 1/2" x 6 tpi. This size will not thread on my shafts. This is 2nd yard that's run into this issue. Current nuts are fine, but I think I'd like spares for something this "weird". The shaft drawing in my GB manual says it takes 1 1/4" x 6 tpi BSF nuts.

Boat is currently at Grand Banks yard in Stuart, FL and yard manager is going to email hull number to factory and see if he can get any information. I've tried Googling that size and nothing really turns up (except BSF is an uncommon thread pitch).

Any GB owners aware of this issue? Thanks!

Fred Boykin

 

[KnotYet]

My 2000 GB42 has an uncommon thread size and standard 2" shaft prop nuts don't fit. Common available size is 1 1/2" x 6 tpi. This size will not thread on my shafts. This is 2nd yard that's run into this issue. Current nuts are fine, but I think I'd like spares for something this "weird". The shaft drawing in my GB manual says it takes 1 1/4" x 6 tpi BSF nuts.

Boat is currently at Grand Banks yard in Stuart, FL and yard manager is going to email hull number to factory and see if he can get any information. I've tried Googling that size and nothing really turns up (except BSF is an uncommon thread pitch).

Any GB owners aware of this issue? Thanks!

Fred Boykin

McMaster-Carr has 1.5" nuts in 4,5,6,8 and 12 tpi in bronze, SS and other metals.
A coarse thread that big should be pretty easy to gauge accurately.
Next day delivery is available in most areas, too. They take returns if you get it wrong.

 

[Comodave]

Maybe go to someplace like McMaster Carr and order one of each size that is close and thread count in ordinary steel. Try them out and when you find the correct size order the bronze nuts.

 

[Larry M]

I ran into the same thing with a sailboat we had that was built in Taiwan. What we found was that the shaft thread and nuts were cut locally and were a non standard size. We lived with it till I replaced the shaft because of wear at the stuffing box.

 

[FBoykin]

McMaster-Carr has 1.5" nuts in 4,5,6,8 and 12 tpi in bronze, SS and other metals.
A coarse thread that big should be pretty easy to gauge accurately.
Next day delivery is available in most areas, too. They take returns if you get it wrong.

Thank for the tip, but doesn't look like McMaster-Carr has that nut in 1 1/4" x 6 tpi.

 

[KnotYet]

Thank for the tip, but doesn't look like McMaster-Carr has that nut in 1 1/4" x 6 tpi.

Ah, I misunderstood. That one is a bit odd. I would try to measure it to be sure.

 

[MVSeafarer]

Local machine shop. It’s a 55 degree thread form. Won’t be cheap but easy to make.