Stuck Powerhead

[iwombat]

Anyone have any tricks for getting a powerhead off an exhaust adapter? '77 85hp is what we're working with. Seems to be hung up on the two exhaust studs. Heat, tapping, four-letter words - no luck. Right now it's sitting in some pb blaster, but there doesn't seem to be a very good way to get oil to where it needs to go. Entertaining any and all advice at this point.

 

[Dhadley]

Re: Stuck Powerhead

We've had to split the housing around the studs and then weld it up later. Rare, heat will usually do it. Are you sure it's not stuck on the d/s splines? I'm assuming it's not, I'm sure you see the front of the powerhead coming up slightly.

 

[iwombat]

Re: Stuck Powerhead

Since the LU is off, I can pretty much guarantee it's not binding up on the driveshaft. And yes, I can see it splitting up front. I've got the exhaust cover off and I'm heating both sides of the studs. I think a bigger boomer and a 2x4 may be the next method.

 

[Dhadley]

Re: Stuck Powerhead

After I wrote that this AM it ocured to me that you probably had the LU off already. Anyway, we've had to split the adaptor but only a couple of times. We've seen more than a few of the blocks broke where the stud is threaded in. That's a little trickier to fix although it can be.

We've also heated the stud itself and had some success with that breaking the salt / corrosion loose as it cooled. Good luck! Let us know how you make out.

 

[iwombat]

Re: Stuck Powerhead

Since I'm swapping, blocks damage to the one I'm taking out wouldn't be the end of the world. I'll avoid it if at all possible though. I may just have to get a second torch so I can heat them both up at the same time and give it a couple of good whacks. Barring that, I may be taking out the sawzall and relieving the block of the stud mounts.

I have a good block welder I use for blown sportster cases. I restore some of the real gonners for a couple of race crews on occasion. "You blew the front half out of the crankcase? I think that's fixable."

I think the cause of all this was the lack of an anode (until I acquired it). So far, every stainless fastener has needed heat to break it free from all the caked on aluminum oxide.

 

[F_R]

Re: Stuck Powerhead

Yea, I reckon you proved one thing: Stainless is not a corrosion cure-all. They actually corrode in aluminum worse than plain steel does. And once they do and you break them off, they are harder to drill out.

 

[iwombat]

Re: Stuck Powerhead

I hear you on that front. It's also the non-threaded part of the fastener that has the most problems freezing in. Smaller clearances and no place for the al-oxide to go. I wonder if the fasteners were threaded all the way up if the problem would be so bad.

 

[iwombat]

Re: Stuck Powerhead

After whacking hard enough to crack the adaptor plate, I decided to go to plan B.

I hated to do it, but I ended up cutting the block. It should be repairable w/o too much hastle. One cut I left a lug to get welded back in. Another, there's about 1/8" gap to fill and deck.

Those studs are still stuck into the adapter plate though. Glowing red-hot with the torch and a pair of vice grips just snapped off the exposed pieces. No way those things were coming out normally. Talk about an ordeal!

Now, I have to see if rounding up another adaptor plate is going to be cheaper than fixing the one I have.

 

[CharlieB]

Re: Stuck Powerhead

Now that you have the block out of the way, a combination of heat and vibration may work.

I've used my cheap air chisel with a blunt nose tip, carefully mark, punch and drill a divot to bang against, heat the ONLY mid til it 'just' starts to blister, use a cutting tip or larger, want it HOT right NOW, and carefully bang away with the air hammer while partner maintains the heat.

The higher freq works much better than swinging a big club.

Oh, and the cheaper air hammer the better, same reasoning, high freq, smaller club.

Oh how I used to cringe to see an old OMC come into the shop after years in the salt.

 

[iwombat]

Re: Stuck Powerhead

Nothing short of drilling the studs out worked, never seen anything w/o threads so stuck before.

After shopping around for a replacement adapter, it turned out the weld and re-deck was the cheaper way to go. The welder gave me a quote of $35 to fix the block too. So, once I decide what to do with the old block I can make that choice.

Thanks for all the advice, fellas.


Anyone want a slightly hacked on '77 85hp powerhead?

 

[JCF350]

Re: Stuck Powerhead

Nothing short of drilling the studs out worked, never seen anything w/o threads so stuck before.

After shopping around for a replacement adapter, it turned out the weld and re-deck was the cheaper way to go. The welder gave me a quote of $35 to fix the block too. So, once I decide what to do with the old block I can make that choice.

Thanks for all the advice, fellas.


Anyone want a slightly hacked on '77 85hp powerhead?

Sorry I was late on this one. Where you using a propane torch? (not enough heat) need oxy/acetylene. Stainless is also easy to drill- use slow bit speed 150 rpm or so and oil if needed, stainless only gets hard when it gets hot.

Used to do this kind of stuff everyday when working for a dealer.
BTW what "corrosion" you see around stainless fasteners is actually "salt water compaction" when you reassemble coat the fasteners with a non hardening brush on gasket glue to keep the salt water out space between the fastener and the hole, Do not do this on head,case or internal engine bolts.

 

[iwombat]

Re: Stuck Powerhead

The salt water compaction is a fine theory, except until June this was a fresh water only motor. Its got classic electrolysis written all over it. I started out with a mapp gas torch, then moved over to the oxy/acetylene. Got the studs glowing red, and still no dice.

Anyway, the whole thing is behind me now, and I'm off to the races putting on the new powerhead tonight.

Roger-wilco on the non-hardening sealer.

 

[JCF350]

Re: Stuck Powerhead

The salt water compaction is a fine theory, except until June this was a fresh water only motor. Its got classic electrolysis written all over it. I started out with a mapp gas torch, then moved over to the oxy/acetylene. Got the studs glowing red, and still no dice.

Sorry, one more question on process for every ones benefit. Did you wait for the studs to cool after heating? I have seen many, many people try to remove them without waiting for them to cool. When you heat a fastener it expands and compresses the corrosion around it then you have to wait for the fastener to cool and contract back to size. Usually, I have always heated the aluminum sometimes almost to the point of flowing but it takes a lot of practice to this. There have been times we have heated spark plugs on Merc 888's then pushed a funnel over them and shot CO2 down the funnel then jumped on them with a socket before the plug got warmed back up from the head temp to get them loose.

 

[iwombat]

Re: Stuck Powerhead

Hot, cool, warm you name it. Would have gone for the dry ice too if there was a decent way to apply it to just the studs. This was a real head-scratcher. I thought about heating the AL w/ the oxy-acetylene but I'm not that experienced in walking the hairy edge. I didn't want to learn the hard way.

The kicker was how hard it still clung to life after a paper-thin wall was left on one side and none on the other. I still had to whack what remained of the stud on the underside to get what was left in the hole to break free and peel off. What a bugger!

 

[JCF350]

Re: Stuck Powerhead

Yep that stuff will make you learn patience.

Glad you succeeded.