Broken bolt on upper stern drive cover

[robinsbd]

I was getting some work done on my stern drive and the technician broke one of the stainless bolts in the top cover. Just wondering if you have ever seen this issue before and if there’s been success getting it out.

Thanks,
Brian

 

[harringtondav]

That's ugly, but repairable. "The Technician" or his employer should be responsible for the fix.
Curious questions: Why was this cover removed? What other repairs lead to this? Are you attempting the fix?

I'd pull the drive shaft assy first, and then the drive shaft, driven gear shown to avoid contamination from the broken screw extraction. Then, clean the top of the hsg with acetone. Then use aluminum duct tape to cover the top bore.

1) The easiest fix is to drill the broken stud and use an "easy out" extractor. Grind the broken stub flat so you can get a center punch divot right on center to start the drill. Use heat, severe hot heat around the stump so the extractor has a chance of breaking the stump loose. But don't break off the extractor, or you'll be in real trouble. If in doubt, go to step 2.

2) It's critical that the first drill is near dead-nuts on center. 'Cuz if the easy out fails, you'll have to drill out to tap drill size and either use a cape chisel to break out the remaining stump, or re-tap, chase tap the remnants out.

If you have access to a MIG welder with SS wire (I do) I'd first try welding a SS bolt or rod onto the stump and turn it out...with that extreme heat. If that fails, go back to the drill out fix. (1 or 2)

Worse comes to worst, helicoil. But an exactly centered drill-out is essential.

 

[robinsbd]

There was an oil leak coming from the drive. It was suspected to be originating from the shift shaft seal. The shop recommended replacing all the seals. So, that’s what they are working on. In their words, they call it “reseal complete upper and lower”. They said they would fix the broken bolt issue, but they will add an extra hour of labor.

 

[robinsbd]

Harringtondav,
Thank you for the detailed response. I’m with you. That sounds like a good plan of attack.

 

[achris]

What I'd do to get a punch right in the centre is to grind the broken stud level, Then, leaving the drive shaft in place, put the cover back on with the 3 remaining screws. Then use a 'transfer punch' to punch the broken screw.... That should make a very well centred punch mark, and starting point for the extraction process.

Also, not a fan of 'easi-outs'. Their problem is that as they screw in, they actually spread the screw you're trying to remove, making it tighter. I prefer to just heat it up nice and hot, a few times. The reason it broke was that water has gotten into the threads and started the corrosion process. Heating it up will drive the water out and allow the screw to turn with a lot less torque. I'd drill and tap a smaller hole and use a high tensile bolt. Loctite it in with red locitite, then wait overnight, next morning, unscrew the stud.

BTW, don't get bulldozed into paying that extra hour. In that position, no excuse for breaking that screw off. That tech was being 'ham-fisted'... He would absolutely have known it was too tight. He should have stopped and hit it with a)heat, and b) a hammer (helps break the bond of the corrosion. Done it plenty of times myself)....

Chris.......

 

[Lou C]

Also...
they should be coating the threads of the bolts with Merc Perfect seal, to keep out the water. I have done this on the Cobra for years and never broke off a bolt head even with 100 % salt water moorage. The sealer keeps out water and does not cause galvanic corrosion as anti seize can.

 

[kenny nunez]

I have encountered that problem with that exact bolt. I always broke them loose with a “T” bar not an impact wrench. A torch had to be used plenty times. Quite often the threads “galled” on the way out no matter how much heat or penetrant that was used.
The best tool for when they did break was a hardened drill guide which most times gets the hole centered using the cover to locate it. Also ended up drilling to the tap size or to a point where there is just a shell and carefully with a small “hog nose” chisel chipping the pieces out. Or just drilling for a “helicoil”. Like stated before. There is always different ways, just hope you use the best one first, along with a drill press or a mill. Any time I broke a bolt I always never charged the customer to remove it.

 

[scoflaw]

It's galvanic corrosion that leads to this fetching up. Stainless in aluminum, I use tef-jel on threads of dissimilar metals

 

[porscheguy]

Is that corrosion or fouling on that case?

 

[Rick Stephens]

Being a welder, my fix, since the stub is still stickin up a little, would be to set a 3/8ths nut on top of the stub and weld it right to the stub through the hole in the nut. The extreme heat expands the bolt and breaks loose the corrosion. When it cools and shrinks it will unscrew, often by hand. I got a broken water pocket bolt out that way last I used that method on an Alpha 1.

 

[kenny nunez]

Granular expansion is the most common cause of stainless bolts in aluminum binding up.
I have in the past had luck welding a nut to a bell housing pivot bolt that was reamed out.

 

[Bt Doctur]

Forget the easy break tool, file what left flat, install the top cover, using a 3/8 punch tip ,center punch and then drill it out and retap

 

[achris]

Granular expansion ....

I'd love a definition of this.... All I can find on a google search is thermal expansion of granular materials, which has no relationship to galvanic corrosion... And the mechanism of corrosion in this case is not by galvanics, it's by water leaching into the cavity between the screw threads and the threads in the hole. Then the water evaporates away, leaving just salt, the next time the boat is in the water, more salt water leaches in and the cycle begins again, but each time the salt concentration increases. Eventually it ends up being so concentrated that the salt abrades (by thermal expansion and contraction) the anodizing on the aluminium and only then galvanic corrosion start.

When I install new drives, one of the jobs is to remove each and EVERY screw on the drive and transom housing, one at a time, and coat them with 'Aqua-lube', and put them back. A few months ago I had to open up my 12 year old drive for a seal replacement. ALL the screws came out like they'd been put in yesterday. I also replace any screws I can see on the engine and inner transom plate that aren't 316, with 316. These include the nuts and washers on the ends of the studs holding the inner transom plate to the gimbal housing, the screws holding the shift plate to the exhaust elbow, the screws holding the ECU to the other exhaust elbow, the screws holding the water pump pulley and the crank pulley to the water pump and harmonic balancer respectively.

Yes, it costs me time and money, now. But the time and money I save when I need to get them out for a repair is paid for many times over. If it costs me $100 in screws, nuts and washers, and it saves just one bust-off, it's paid for itself. Not just in terms of money, but more importantly, frustration.

Chris......

 

[kenny nunez]

2Xs on Chris’s way of using a Never Seize type compound.
The old OMC drives used 1/4” 20 bolts that really were hard to remove and would break just about every time. Sometimes by the time I had the drive taken apart the it looked like it had been in a fire from all the burned paint. I even had to “bottom tap” the holes to get the build up out of the threads.
Several times I would get one back after a few years and had no problems with the small bolts with the Never Seize.
The “Granular Expansion” term was explained at one of the OMC dealer seminars back in 78.
One thing about the AQ Volvos was that I very rarely had to light the torch.

 

[robinsbd]

Everyone, this is why I love this community. You guys are awesome. Thank you very much for the excellent discussion and analysis.

 

[scoflaw]

Been doing this long enough to know the "salt leaching" theory is just as crazy as "granular expansion".

Regardless of the term used the solution is the same, clean the threads and put the goop of your choice on them

 

[achris]

Been doing this long enough to know the "salt leaching" theory is just as crazy as "granular expansion".

The salt water gets into the threads, that is not a 'theory', that is a fact.

Chris.....