Head Bolt 305027 Size?

[robfurman]

Does anyone know the diameter and pitch for head bolts on a 1966 Johnson Seahorse? Part Number: 305027 from:

http://www.marineengine.com/parts/v...ntage-evinrude-johnson/382080/38208000001.htm


thanks,


Robert

 

[Daviet]

Re: Head Bolt 305027 Size?

Sorry, off of the top of my head, I don't know. Why don't you pull one and measure it?

 

[robfurman]

Re: Head Bolt 305027 Size?

Sorry, off of the top of my head, I don't know. Why don't you pull one and measure it?

I wasn't at home when I posted this and I was hoping to order a thread repair kit, but it appears that they are a 7/16" x 18 pitch.


Robert

 

[Tim Frank]

Re: Head Bolt 305027 Size?

I wasn't at home when I posted this and I was hoping to order a thread repair kit, but it appears that they are a 7/16" x 18 pitch.


Robert

Don't think so, that would be a "special".

7/16 NC would be 14 TPI (i.e. 7/16-14NC)....and that is a big cap screw for an O/B head.

I'd bet they are 5/16-18NC.

What size Johnson?

 

[robfurman]

Re: Head Bolt 305027 Size?

Don't think so, that would be a "special".

7/16 NC would be 14 TPI (i.e. 7/16-14NC)....and that is a big cap screw for an O/B head.

I'd bet they are 5/16-18NC.

What size Johnson?

my bad, I had meant 5/16-18. This is for a 60HP Johnson Seahorse (vxl-12r)



Robert

 

[Tim Frank]

Re: Head Bolt 305027 Size?

my bad, I had meant 5/16-18. This is for a 60HP Johnson Seahorse (vxl-12r)

I wasn't at home when I posted this and I was hoping to order a thread repair kit, but it appears that they are a 7/16" x 18 pitch.

Robert

Yup, 5/16".

Since I am responding anyway, from the "Cliff Claven collection of superfluous and unasked for info," pitch would not be "18"....pitch is distance between thread crests so for a 5/16" NC thread, pitch is 1"/18.

This actually sometimes is useful....a 1/4-20NC thread (or a 1/2-20NF), really common, has a pitch of 1"/20=50 thou. So One turn of that thread gives you .050" reference....1/2 turn = .025 . etc.
And 1-8NC has pitch of 1/8" = .125" , another useful reference.

Norm, pass me a beer....

 

[robfurman]

Re: Head Bolt 305027 Size?

Yup, 5/16".

Since I am responding anyway, from the "Cliff Claven collection of superfluous and unasked for info," pitch would not be "18"....pitch is distance between thread crests so for a 5/16" NC thread, pitch is 1"/18.

This actually sometimes is useful....a 1/4-20NC thread (or a 1/2-20NF), really common, has a pitch of 1"/20=50 thou. So One turn of that thread gives you .050" reference....1/2 turn = .025 . etc.
And 1-8NC has pitch of 1/8" = .125" , another useful reference.

Norm, pass me a beer....

Getting down to why I asked this question. I need to order a thread repair kit for one of the bolt holes that is stripped out. I have not seen any sites list a kit for a 5/16" NC, but they do list a 5/16-18. Seeing this will that be a correct fit?


Robert

 

[Tim Frank]

Re: Head Bolt 305027 Size?

That will be the correct kit.
5/16-18 is a coarse thread (National Coarse, NC), the 5/16 NF (National Fine thread) is 24 TPI