lower shock mount bolt broke...now what?

[glennwingman]

While trying to remove the shock absorbers on my 1980 merc 90, to replace them with the ptt system from my 76 650, I broke the head off of the bolt that goes INTO the lower shock mount pin. I cant get the pin out, and I cant seem to find any information for this online. Anyone have any ideas of what I should do, besides trying to drill and retap the hole?

 

[RLT III]

Re: lower shock mount bolt broke...now what?

I think you got the right idea good luck

 

[Chris1956]

Re: lower shock mount bolt broke...now what?

The bolts are stainless steel, 1/2" fine thread. Make sure you use the best drill bit (cobalt or something better), as the SS is hard to drill. I would also recommend that before you try an easy out, you heat the pin red hot, remove the heat and apply some good penetrating oil to the bolt. Maybe you will get lucky and the bolt will unscrew.

 

[Chris1956]

Re: lower shock mount bolt broke...now what?

Are you sure the PTT unit from the 650 will fit? If so, the triple clamp from the 650 will fit as well. You might just switch them, especially if you have trouble getting the bolt out.

 

[sschefer]

Re: lower shock mount bolt broke...now what?

I just went through this with a mid section. I found a guy with a EDM that was able to remove the majority of the bolt material and then I was able to pick the old threads out. Mines good as new. You do have to disassemble the unit but the same goes if you're going try and drill it out. You'll have to do it on a drill press with very little, (preferably no), runout or you'll end up with a worse mess than you started with.

Alternatively, you can drill it out completely and use heli-coil to restore it. The key there is that the more accurate your drilling process the better it will hold.

If there's enough material left to get a hold of then try the heat like achris say's first. There's also a product called Freeze Off by CRC that is supposed to cryo freeze the corrosion and cause it to fracture but it didn't work for me.

 

[glennwingman]

Re: lower shock mount bolt broke...now what?

by triple clamp do you mean swivel bracket? I could check, although I wanted to sell the 650 as im only re-powering to get a bit more power. the 65 is still good and I wanted to sell it whole.

 

[Moody Blue]

Re: lower shock mount bolt broke...now what?

Did the bolt break at the head or flush? Were you able to remove the shock?

I've had good success with seized bolts using paraffin wax. Heat the housing up pretty hot then apply paraffin wax to the broken bolt as it cools. The liquid wax will be drawn into the threads providing lubrication to help free it. At the same time, rap the housing with a hammer (not TOO hard) to provide vibration and help with the wax penetration.

After it cools, use a die grinder or dremel tool with a cutoff blade or small carbide burr, and cut a slot across the broken bolt face. Use a LARGE flat bladed screwdriver and a pair of vise-grips clamped to the shaft. Try to turn the bolt both directions, just a little at a time. WIth any luck you should be able to work it free. If the bolt shaft is exposed, TIGHTLY clamp the vise-grips onto the bolt shaft and work it both directions just a little at a time.

 

[glennwingman]

Re: lower shock mount bolt broke...now what?

the end result of this adventure involved me heating the swivel bracket with an oxy-acetylene torch, then using an air chisel in a slot I chiseled into the pin. I tried removing the bolt, nothing budged it. It broke off slightly inside the pin. Aluminum inside steel inside aluminum, what a great idea! I was lucky to find a pin at my local dealership, they're unavailable from mercury. Final thought. BE CAREFUL REMOVING YOUR SHOCKS! If the bolt doesn't want to come out, spray some oil on it, let it sit. Its NOT worth the $50 pin, or the hours of your time to remove it.

 

[Chris1956]

Re: lower shock mount bolt broke...now what?

Those shock mount pins were tool steel, mounted in the forged aluminum triple clamp. I also think they had a bolt or two, to keep them in place. The bolts were SS.

 

[glennwingman]

Re: lower shock mount bolt broke...now what?

someone had replaced the stainless bolt with an aluminum one it turns out! The other side was steel, which made me not even try to drill it out, but it turns out this side was aluminum, thats why it broke. Some people...well, its all fixed, heres the end result! Thanks all for your help, and pray this never happens to you.
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