Exhaust bolts

[basstracker1970]

Can someone please tell me what size the 18 exhaust bolts are on a 1983 80hp mercury. The old ones are rusted and want to replace them. Thanks in advance.

 

[carholme]

Re: Exhaust bolts

basstracker;

These ones, item 23, are 1-1/8" long

http://www.crowleymarine.com/mercury-outboard/parts/678_100.cfm

Gerry

 

[basstracker1970]

Re: Exhaust bolts

What are the thread size of them like 1/4 x 20 something like that ? I know they are bigger than the 1/4" as I ordered new water jacket bolts and they were 1/4 x 20 x 3/4".

 

[carholme]

Re: Exhaust bolts

basstracker;

Sorry, I'm not anywhere near my shop right now but if you have a tap and die set, there is usually a pitch gauge in the kit.

Gerry

 

[basstracker1970]

Re: Exhaust bolts

Ok I got my tap and die set out and fig out that it's a 5 \16 size bolt but what does nc18 mean? Is that the thread size 5\16 x 18 bolt?

 

[wifisher]

Re: Exhaust bolts

nc stands for "national corse" yes 18 tpi. It is the standard pitch on 5/16 bolts available almost everywhere. If you look at your other dies/taps you will see that they are all either "nc" or "nf" i.e. fine thread which is 24 in the case of a 5/16.

 

[basstracker1970]

Re: Exhaust bolts

Thanks alot wifisher and carholme I got it now. I ordered me a set of stainless steel bolts for the exhaust covers and the water jacket covers.