1960's-1970's Johnson Evinrude screw threads

[johnson_nut]

Hello, I was wondering if anyone knew what threads 60's and 70's johnson,evinrude outboards use. I tried one in a whitworth die and it seemed to run through. But i am not sure as the amount of thread types confuses me!

Thanks

 

[Scaaty]

Re: 1960's-1970's Johnson Evinrude screw threads

Should be straight SAE......not Whitworth. Which bolt are we talking about here? Every old Johnny I have worked on was staright SAE course or fine.

 

[johnson_nut]

Re: 1960's-1970's Johnson Evinrude screw threads

G'day
The head bolts are the ones i tested. SAE makes sense. sae and whitworth must be similar enough to let the bolt run through the die.
Thanks alot.

 

[F_R]

Re: 1960's-1970's Johnson Evinrude screw threads

The usual practice is that coarse threads are used wherever screws and bolts go into aluminum. The smaller sizes are 10-24 1/4-20 5/16-18 and 3/8-16 The 10-24 being a "number" size, and the rest being fractional inches. Fine thread sizes are 10-32 1/4-28 5/16-24 and 3/8-24

 

[cid]

Re: 1960's-1970's Johnson Evinrude screw threads

Any guess as to the thread size on a '70 4Hp where the recoil bolt attaches to the block? Mine is pretty rough and Im either going to chase it and try "one last time' or Im going to have to resort to an insert of some type
thanks

 

[Paul Moir]

Re: 1960's-1970's Johnson Evinrude screw threads

The little one is a 1/4"-20tpi. Do you mean that one or the big one?
The big one is 5/16"-18tpi.

Helicoil or some such insert is the best way of fixing bad threads. I can see how the big bolt may have been cross-threaded.

 

[cid]

Re: 1960's-1970's Johnson Evinrude screw threads

Its the one that holds the recoil together and bolts through the center of it to the block.
I am still waiting on a piston, think I found one out of Ishopmarine. every one tells me they dont make these any more. :'(
Thanks

 

[Paul Moir]

Re: 1960's-1970's Johnson Evinrude screw threads

EDIT: Sorry, running off topic here. Posting to other thread.