BOLT head in the Bilge...

[Perseverance]

8.8 refers to the hardness and indicates that it is metric probably 10 mm. Can be one of two thread pitches. 8.8 it the most common of hardened metric bolts and should be easy to find.

[SloopJonB]

Originally Posted by PorFin

Monkey,

If you can manage to get a scissors jack under the engine, you can fit it up to support it when you remove the bracket.

Otherwise just use wedges - you can exert an amazing amount of force with wedges so be careful to just make them snug, don't pound them in. If the engine does settle a little - enough to make lining up the new bolts a problem, just tap the wedges some more until it rises into position - you can be very precise with them.

[TQA]

As others have said you need to fix it now.

Replace BOTH bolts. If possible get aircraft quality bolts.

The broken bolt might very well come out easily but if not heat is your friend. Get someone with a gas axe to come along and heat up the casing. Fire extinquishers at the ready of course [or a water hose].

[ecarter517]

The good news is that you found the head and it was in the bilge. I once found a 3/8 washer on my deck while sailing off the coast of Baja California. Heads popping off on steel bolts is usually not due to direct stress, but due to hydrogen embrittlement (a manufacturing/processing defect). Other bolts that may have come from the same lot should be considered suspect.
I have made this type of repair several times, and it is unlikely that you can back out the bolt with vice grips, but its worth a try if you can do it while leaving a good bit of the broken bolt protruding. In any case you will need to remove the bracket first. In drilling for a screw extractor (easy out), the hard part is drilling a hole in the broken bolt without running it out into the surrounding part. I would make two drill bushings. Each of these would be a short piece of steel rod with a shallow hole in one end that would fit over the broken bolt extension (there needs to be an extension left) and the first would also have a hole the rest of the way through that would be a close fit for a center drill. This would be used to drill a center into the broken bolt. The second drill bushing would be the same but with the through hole the size to guide the drill for the easy out and used to drill an appropriate sized hole deep into the broken bolt. If you end up just drilling out the broken bolt, it is extremely important to keep the hole as centered over the original bolt as best possible. Good luck

[hellosailor]

Another couple of options: Oddly enough, an old basketball or soccer ball makes a decent air jack. Deflate, stick under the engine, pump up until it starts to lift.

Once you remove that engine mount, and put some PBlaster or other real penetrant on that stud, you may also be able to unscrew it by cutting a slot in it (with a metal saw blade or dremel bit) and then hitting it with an impact hammer and a "screwdriver" tip. If the penetrant has done its job, that will spin right out with the impact hammer. If not...you can still use the screw extractor.

Note the position and alignment of the motor mount carefully, try to match it back up since that affects shaft alignment. In theory, engine mounts should be replaced about every five years as the rubber stiffens up or cracks over time. In practice...that's something else again.

Could be that bolt sheared because it was improperly torqued, so if you have a torque wrench, use it. If you don't, this could be the time to buy one anyhow. And I suppose if you were really compulsive, you mght want to replace both bolts on both front mounts while you're in there. Using Loctite or antiseize on all of them as well.

Or just replace the one and go sailing.

[dorymate1]

most of the time heads come off bolts because the bolt was loose in the first place. this usually occurs because of poor engine alignment. The stud in there may back right out buy hand if you get the mount off. You can take the weight off the mount many ways. The wood blocks and wedges is most likely the easiest. Have a experienced tech inspect your mounts and replace them if needed carefully inspect your shaft & cutlass brg. then have your engine aligned. It needs to be within .003 tolerance. When running your engine in gear a good alignment will have no noticeable vibration. One trick to checking vibration is to set a cup of water on the cockpit sole if you see concentric rings in the water you have vibration. The better you get the alignment to longer all your machinery will perform & last.

[captainbri]

one other way of getting a bolt out is to freeze it, coke also eats rust, a butane torch really doesn't get it that hot. it may be a stud and once you remove the bracket you might have enough to grip it. you can drill out a hole in the center and use a screw extractor set.

one trick is try to tighten the bolt then spray wd40 on it then try to loosen it.

[captainbri]

depending on how much of the bolt shoulder is sticking out, you can use a chisel and hammer to make it turn. you want to walk it around you do not want to use it as if you were using a screw driver to turn it. basically the chisel would be flat against the block so when you hit it with the hammer it turns the screw.

[chucklesR]

Sometimes simple is better. If you have a bit sticking through dremel a slot or an 'X' and take it out with a screw driver (of course penetrating oil etc.. first)

As others have said, I'd replace all of the bolts, but first I'd call the service who did the realignment and tell them they have some explaining to do, followed by a refund or repair. This didn't happen because they did the job right, not in a couple of months.

[SloopJonB]

I'm betting the shaft of that bolt is stuck really tight. I've found over the years that the single biggest reason for bolt heads failing is over tightening - someone leaned on the wrench until they felt the bolt head start to give and called it good enough.