115 johnson repair issue -pistons-

[mekkamaz]

Hi everyone:

I?m reboring my 1980 115, and have all set to get in pistons and all stuff, but an issue has jumped on me..

The repair shop that has worked on the motor, when cutting the cylinders to .030", didn?t reach all the way to the bottom of the cylinder (not noticed till try to assemble, you can figure my reaction), so now when I?ve tried to assemble, crankshaft does not turn fully cause there?s like 3/16" at the bottom of the cyl. smaller than the rest (cause the cutting tool didn?t reach the bottom). That?s in all 4 cyl....Measure pistons and they all are in specs...identically to the old ones.

Anyway, went back to the shop and they can?t reach further, and there?s no other shop around to do it so...

Ok, they offered me a couple of solutions:

1.- Work the piston skirt with a grinding wheel at the mere bottom in order to get fully down the piston or..
2.- Work them on a lathe and cut the bottom of the piston to make that part smaller to make it fit...

Well guys,need your (as always) great advice and knowledge....what should I do?? any other idea or solution??

 

[Capt Ken]

Re: 115 johnson repair issue -pistons-

Then they are not much of a machine shop. Do not tamper with the pistons. They are balanced and you will only make things worse. Even if you have to ship the block off, get it bored correctly. What did they use to bore it with? They should be using a rigid hone and it will cut to the bottom.

 

[V153]

Re: 115 johnson repair issue -pistons-

Then they are not much of a machine shop. Do not tamper with the pistons. They are balanced and you will only make things worse

Agreed! Have them complete the job, at your own risk. Or demand your money back'n then bring the block to a shop that can bore it correctly.

 

[mekkamaz]

Re: 115 johnson repair issue -pistons-

Yep, they used a rigid hone, in fact it is a boring machine and they mostly do 2 cycle motors for bikes and mowers...and it is the only shop around here (yeah, there are some other automotive ones but all rejected the job on this V4 2 cycle)so I think that send it away it is the best and maybe only option....aaarrrrggghhh!!! more time away from water!!!!!

 

[Faztbullet]

Re: 115 johnson repair issue -pistons-

You cannot bore a blind hole with a Sunnen honing machine you must use a boring bar, thru cylinders like mowers,bikes ,ski-doos there ok to use on. If you cannot find someone local to repair it pm me and I can do it or send to Mar-fab for repair. You may have to go the next size up if cylinder is tapered at bottom as this is only way to cut it true.....

 

[mekkamaz]

Re: 115 johnson repair issue -pistons-

Thanks to all for your priceless answers. really appreciated.
As always you guys rock!!! Following your wisdom I search and found a little shop but with a guy with experience.....push the piston all way in and found that it was a little bump in one side of the cylinder wall that was stopping the piston....yeah, I know...I also think that the shop that makes the job sucks....anyway...this far we use a sand paper and just a little work and voila!!! they travel free!!! We measure the cylinder wall (with a micrometer) and there are ok, no tapered at all...within specs (well, this part the shop did ok,though)..just like Faztbullet says, they didn?t have the right tool for the job and they miss the bottom in a spot....and the problem was only one bank, meaning two cylinders, the other two were ok..so I?ll start assembling and I hope to get all done right from here. Again, thanks!