How to remove a stuck stud on the impeller housing?

[IvanJ]

Today I tried to remove the impeller that hasn't been replaced for like 30 years. I managed to unscrew all bolts, but one of them was seriously stuck and eventually had its head brake off!
I removed the impeller housing, the gasket - everything except that stud. I then tried everything I could - strong HCL acid to melt the lime, WD-40, adjustable wrench and heavy duty pliers... no luck. I hit it with a hammer several times but - it's STUCK! It won't move at all.

What can I do now?

 

[Woodnaut]

Re: How to remove a stuck stud on the impeller housing?

I asuume that this is probably small diameter stuff - either a 1/4-20 or #12-24, and that the stud in stuck in the lower housing. Is that correct? As long as the stud is accessible, I would probably first approach it with a pair of vice grips which were tightened down as tight as I could get them. (You're probably only going to get one shot at this so I would go to the "ridiculously tight" level.) Once you get them on there good and snug, do you best to pull/turn the vice grips in such a way as to rotate the stud rather than just pull the vice grips off of the stud.

If this works and you get the stud out, it's probably going to tear up the threads pretty bad. At the very least you should run in with a tap and chase the threads. If you reassemble with the same size of bolt be careful not to overtighten or the remaining thread area might be destroyed. It might be possible to go to the next larger thread size, but that would really depend on the clearance hole through the impeller housing and wall thickness around the hole in the lower unit. Whatever you go back with, be sure to use some anti-seize on the threads so you son't have to relive this experience. (Just be sure you don't get any anti-seize on any of the gasket surfaces.)

If the stud still won't budge and the vice grips just come off, then it becomes a more difficult problem. If vice grips cant twist it out, it seems that an EZ-out will probably not work either. I've encountered bolts like this before in the past and was able to cut them off flush and then successfully drill down the center and retap the hole. (If you don't go ovesize, the threads may not be very good quality.) This is tricky business, however, because if you get off center the drill will move right off of the SST bolt and into the soft aluminum lower housing unit. Then it's pretty much all over. However, if you use a sharp drill bit and really take your time you can pull it off. Like I said, drilling right down the center of a broken bolt can be tricky business. Maybe some of the other guys have a better suggestion.

 

[CATransplant]

Re: How to remove a stuck stud on the impeller housing?

You can mess with it and mess with it and maybe still not get it out. You could also ruin things badly enough to end up costing you a pile.

My suggestion is that you take your lower unit down to the nearest small machine shop and talk to the owner. Show it to him. He can remove the stud or drill and retap in just a short time. You'll have to pay for it, but I promise you that if you mung things up in a serious way, you'll pay a lot more.

Others will offer suggestions on how to do it yourself, but keep in mind that you can also mess things up enough to cost a lot more than the machine shop will charge you.

I'm just sayin...

 

[IvanJ]

Re: How to remove a stuck stud on the impeller housing?

Thanks!! I'll try something tomorrow with vice grips. If it doesn't work, then I'll handle it to the mechanic.

Yes, it's small diameter and lower housing.

 

[Rocky_Road]

Re: How to remove a stuck stud on the impeller housing?

Working in a Mercury dealership (many years ago), I watched the mechanic weld a nut to the end of the broken bolt. This did two things...gave him something to put a wrench on, and the heating of the bolt would cause it to expand and 'crush' the corrosion around the embedded threads. Once cooled, the bolt always came out with just a little persuasion...!

You can get your hands on a propane torch (or even butane) and heat the bolt yourself. Even without the welded nut to use a wrench on, the vice grips may do the job...once the bolt has cooled, and contracted.

 

[kenmyfam]

Re: How to remove a stuck stud on the impeller housing?

Half decent machine shop will sort you out in about 10 minutes. Try the easier stuff but do not risk messing it up beyond redemption.
I have several machine shops available at our plants that help out when necessary. failing that I take it in and do it myself on the off shift.
Good Luck.

 

[rusirius]

Re: How to remove a stuck stud on the impeller housing?

Rocky has it right... If you can weld a head onto it and heat it pretty good you might have a shot at getting it out...

If not, you can do what I just had to do on 5 bolts during my recent rebuild... (arsehole previous owner PAINTED over the anode... )

First you need to use a dremel or a grinder to grind the rest of the bolt off flush... BE SURE TO BE CAREFUL not to grind the surface, especially if it's a gasket surface...

Next you need a GOOD center punch... Check it twice, three times, even four times.... Make sure you're EXACTLY in the center of the bolt... (be careful, sometimes the "threads" can make it LOOK like you're off center even when you're perfect...

Once you get a good centering hole punched then just start with a very small drillbit (1/8" or so)... And pay close attention here... Make sure they are GOOD and VERY SHARP drillbits... The ones I like to use are specifically made for stainless steel... Just make sure you take your time, go slow, and keep it straight!

Once you have your pilot hole, then you just keep working up in size... When you get to 13/64 (assuming 1/4-20 bolt) then you can run a tap to clear out the excess threads... As you're doing so, just keep going a little deeper and then remove the tap (often times the thread will "wrap" around the tap as it's removed so you have to clear it occasionally... When you're done you'll have a perfect 1/4-20 hole...

IF for some reason something happens and the threads just aren't good, then you can go ahead and drill the same hole with a 17/64 bit and tap it for a heli-coil...

I've done this time and time again and it's always worked perfectly... You DO have to be very careful though! As Rocky said, the bolt is a LOT harder than the surrounding aluminium... So you have to use a very sharp drillbit to keep it from "wandering" off into the aluminum and go very slow...

 

[IvanJ]

Re: How to remove a stuck stud on the impeller housing?

Thank you all!! I hope this post will be useful for anyone experiencing the same thing I did. I managed to pull it with vice grips, it was tough!