Tools.

I've wrung bolts with and without power tools.
I don't usually resort to power unless manual didn't work.
I think that it all depends on how much corrosion has taken place.

 

I try to feel the load on the bolt and watch closely to see if it will turn. I use a plumbers torch to get the area hot if a bolt won't come out. After breaking off a few dozen, one develops a sense of feel and knows when to quit turning and start burning. If you turn a bolt head a tiny bit, but can't detect any space behind the head then you are likely twisting it off. With an impact wrench I think you wouldn't be able to do this and break off more with it. Remember stainless steel bolts can't take as much load as alloy bolts. I have worked with a wrench in one hand and a torch in the other for many hours. When re-installing bolts use anti-seize on the threads. You will be glad you did later.

Best regards,
Frank_S

 

I don't think impact or straight torgue tools will do any good to turn the bolt loose from the motor.

I've always let my outboard motor warm up first until I feel the head bolt is hot then I shut it off.

Spray penstrate oil on it and wiggle the bolt to tight it in and loose it up. Turn clockwise back and forth until u free up the bolt thread inside.

When u feel it's getting loose then take the bolt off slowwwwwwwly.

If the bolt is not going anywhere then go to the next one and try it again later with more penstrate oil with warm motor.

I never had any problems with thermostat, water jackets, intake, and lower units. I just gotta take my time and work the bolts to get it free instead of jerk it off and break it.

 

Do you mean the hand-held-hit-it-with-a-hammer impact driver? Or an air or electric impact gun?

Either way, it depends on the application. Stainless bolts into aluminum, I'd never use anything other than my own hand tools. It's a finesse game, like Frank said. Other things, like flywheel nuts, impact away!

 

I use a small ballpeen and a punch to try to shock the bolts. Rap on the bolt head a few times and then try again when putting pressure on the bolt.

Used this in conjunction with heat, penetrating oil and patience.

As frank said you will get a feel for it. When the bolt starts turning DON'T try to take it all the way out, Do like WS said and slowly work it back and forth. I do this fractions of an inch at a time. Yea it's gonna take you 5, 10 maybe even 20 minutes to work one bolt but, trust me, when you get that baby out intact it's worth it. ;D

I guarantee I would've broken every bolt I tried to remove in the merc if I hadn't used these techniques. Sometimes they're just not gonna come, this morning the welder called me up and said he worked on one bolt for 30 minutes and could not get it (He built up the bolt with stainless rod, tried removing it with vice grips, ended up welding a nut to the bolt and broke that off trying to remove it).

On to plan B: Drill out the bolts, try to save threads. If not, helicoil.

Lesson here?: Don't but a Merc with any broken bolts or signs of corrosion. :-/