What Kind of Bolt is it?

[Pat Crowley]

I am taking apart a 1982 90HP Evinrude and just exposed the crankshaft. The bolts that hold the back part of the piston arm to the crankshaft are not 6 sided. They appear to be round & splined. I count 12/13 splines, each protrudes about 1/32 or less from the head. The size is about 3/8" I could put a 12 sided socket on it but I am afraid to tear it up. My sockets are normal thickness and the bolt head is so close to the piston arm that I cannot get it all the way down. Does anyone know what I'm talking about and what kind of socket or driver it takes to remove the bolts?

 

[cedarjunki]

Re: What Kind of Bolt is it?

spline drive bolts....

ive used an old socket and ground it down a little bit to fit.
or just buy a set of thinner sockets.

 

[wilde1j]

Re: What Kind of Bolt is it?

Typically it's a 12 point thin wall socket. Nothing special. Now if you had an OEM shop manual you'd know that, as well as knowing the cap screws MUST be torqued and good practice is not to re-use the old cap screws, unless you know this is the ONLY re-use.

 

[F_R]

Re: What Kind of Bolt is it?

5/16", 12 point thin wall. You need a high quality socket such as a Snap-On in order to have enough strength combined with such a thin wall. And yes, I've broken some Snap-Ons too. But they have a good warranty.

 

[wilde1j]

Re: What Kind of Bolt is it?

F_R, you're certainly right about the quality socket deal. I broke a couple a lesser sockets before I got smart ... not a tool to cheap out on.

 

[Pat Crowley]

Re: What Kind of Bolt is it?

Thanks to everyone for the quick response. I'll buy a really good quality 12 Point thinwall and give it a try. Just wanted a little re-assurance before going forward. Better safe than sorry, right. Thanks again.

 

[kenmyfam]

Re: What Kind of Bolt is it?

Quality is so important with the thin wall sockets. Don't cheap out.