Best way, remove head bolts?

[Playtime H2O]

Hello,
I am kinda in a bind with this motor. I have a 1985 Merc 150 and I want to pull the heads to inspect it. Last year the motor got kinda tight and we loosened it up by working it back and forth with spark plugs out and PB Blaster sprayed in the holes. Well this year I want to pull the heads and have a look before any attempt to put it in service. I have really bad luck when it comes to unbolting outboards this old. What is the best way to do this? Should I put my 1/2" impact wrench on it and just go at it using the un-torque sequence. Or should I use my smaller 3/8" impact wrench and let it hammer them loose slowly? Or should I just unbolt the head bolts by hand? In the past I have had better luck using my smaller 3/8" impact wrench on these aluminum blocks. I already know I have to use the un-torque sequince to unbolt the heads just as I have to use the torque sequince to bolt them back down. My problem is getting the bolts out in one piece and having usable threads when I want to put it back together. What method do you recommend? And/or should I use any heat to maybe expand the aluminum molecules to assist the bolt removal? Thank You!

[olmo40]

Id just unbolt by hand ,clean threads and light oil for re assembly, In saying that is the power head or bolts badly corroded ?? If they are flaking you would replace them ,sounds like you know that tho

[fyremanbil]

I'd put heat to them if they are tough to get out. Once you break the head off, it's a lot more work to get them out.

[Playtime H2O]

olmo40,

No, they are clean with original paint on them. The motor has very low hours on it but it is still a 1985 150 no matter how I look at it. The motor has never been taken apart and never in salt water. The guy is a fanatic and flushed with fresh water and soaked the thing down with a can of WD40 after every use. I'm thinking that using my small impact with the air regulted down might be a good starting point. Then I'll slowly up the air till they start moving. That "Bull in a China Shop" attitude has never really worked out too well for me when it comes to these old aluminum blocks. I just have bad luck that's all. So I'm here wondering what tricks you guys have.

[kb5050]

if they break off, I've had good luck welding a nut on the broken bolt, gives you something to work with and the heat from welding usually frees up the corrosion and they come out easily

[Playtime H2O]

fyremanbil,
Yeh I used to work as a lawn mower mechanic when I was younger. I used to have to use heat all the time on old corroded up mowers. It bacame a way of life at the mower shop to always have a torch handy.

[flabum1017]

I'd do the bottom two by hand to see if they are froze up, if they come out easy, then you can zip the rest of them out with the 3/8" impact at medium pressure (around 60 psi)

[Jay Smith]

I DISASSEMBLE heads with 3/8" Impact ( 200 PSI air pressure, if the 3/8 impact bogs down I go to the 1/2" er ) I may be lucky BUT I've NEVER had a bolt break off using the impact (s) . I use impact grade 6 point sockets too , they fit sooo tight sometimes they have to be tapped on to go past the paint and crud..

Good luck,
Jay