Temp sender

[Stevie.UK]

Hi guys

My temp sender is on the fritz, I've took it out but there is no shops local to me so I've got to send for one online.
I've got a 1993 Scr 2300 with a Mercruiser 4.3 V6.
From google I believe the engine was fitted with 1 of two size senders either the 3/8 or the 1/2.
The only trouble is in the UK we work in metric so I don't know which it is.
I've tried to put an imperial wrench around the threads but neither the 1/2 or 3/8 fit only the 5/8 fits?
I know it's probably my lack of knowledge but any help on working out the size would be great.

[mmwjr]

The 3/8 or 1/2 is the thread size. 1/2 is darn close to 13mm so use a 13mm to see if the thread section has play or a tight fit.

[Stevie.UK]

I've just tried a 13mm ring spanner over the thread but it won't go over the thread?

Thanks for the reply Mike

[speedysprocket]

That's because those are NPT- National Pipe Thread, which measure larger than their classification.

[Stevie.UK]

Thanks speedy socket but I've no idea how to relate the info in that chart to my sender?
I can fit a 5/8 ring spanner over it but it's quite tight and goes around halfway down the thread. If anyone's got an easy way to tell I would be most greatfull .

[speedysprocket]

You don't have a ruler or calipers to measure the diameter of the threads? Even if all you have is metric, divide your mm by 25.4 to get inches.


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[Stevie.UK]

Just spoke to a an engineer friend who tells me it's a 1/2 inch.
Apparently the measure is the width of the bolt not including the thread part.
Well you learn something new everyday they say lol

Thanks everyone for your input