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I'm replacing the engine beds in my B28, the plywood-boxed mahogany beds are shot from trapping fresh water dripping on them from around hatches.

The stringers are in great shape but have 1/2" (?) bolts through them and the engine beds to hold it all together. These bolts are trash but seem to have basically become one with the stringers, probably from rust expanding. I've pounded on them as much as I can swing in the space but all that does is make a lot of noise. I don't want to try penetrating oil as it will just run down the stringer. I'll soon be epoxying a sister in along the stringers and am concerned about contamination beyond the usual 'under the engine' mess. I'll also be epoxying up these bolt holes w dowel and don't want the stringer wood oily.

Any ideas to remove what remains of these fasteners without too much destruction? I thought about drilling them out but two will be tough to get at because of the raw-water strainers, a few others have been reduced to 'points' by corrosion so it will be tough to start a hole in the end of the remaining bolt. A small hole saw to cut around the bolts won't work as it would have no center to follow. Maybe a small drill bit around the circumference of the bolt to loosen it? I don't have a compressor there so I can't use a die-grinder and carbide.

Any suggestions would be appreciated! Thanks in advance.

You can get small hole saws from Grainger like https://www.grainger.com/product/29VT97 ... 25160558:s If there is some bolt left you may be able to remove the pilot bit and let the hole saw settle in on the fiberglass around the bolt.
Or any chance to press them out with a clamp around the stringer or by using https://www.harborfreight.com/10-ton-su ... 62114.html pressing from the opposite stringer?
Alternatively, as you plan to epoxy a sister over where the bolts are - just grind them flush and we will never speak of this again?
Good luck,
Stephan

On another note, I just bought one of these, and it's a beast.



https://www.ryobitools.com/products/det ... ss-grinder

There is a slower, less expensive on as well.

https://www.ryobitools.com/products/det ... le-grinder

you can get around a wandering hole saw by starting with a solid piece of board, drilling the hole through that, then clamping the board over the spot you want to drill out. From there you can take out the center bit of the hole saw and the board will act as a guide so you drill in the correct spot.

As mentioned above, really comes down to are you re-using those holes or putting holes in very close proximity. If not and you are going to sister both sides, grind flush and move on. It may be a good idea to mark the locations with permanent marker or paint just in you might need those locations in the future. Wouldn't want to start drilling and and then remember that there is some steel in the way.

If going to re-use holes etc., KTM's idea is great. Use a big enough hole saw so that any drilling will not be close to the perimeter of the plug and make sure your hole saw is deep enough to go through the stringer as you will probably not be able the chip off layers with the bolt in the center. Once you have the hole started per KTMs instructions, you can then remove the block to gain back some whole saw depth if needed. Would want to avoid having the drill both sides of the string trying to match up the holes.

When I did mine, I found that by putting socket on them I was able to spin them with a breaker bar. Once I got them to spin, they either backed out on their own or I had ss second hand who would turn them as I hit them with a small
Hand sledge.

I did exactly what Tony did and they came out one got stubborn and it was rotted pretty good so I used a little pipe wrench to turn it.

Use mike olsteins tool,
Cut off the bolt heads and drive the bolts out with an awl

Thank you all for suggestions! There's not much nut left on these and the bolt outside the stringer has rusted to a taper so it's hard to turn them, thought about the holesaw with plywood guide but would have to remove raw-water strainers to have a straight-on shot at two of them, I'm sure pressing them would work but would need appropriate tool or fab something...

I wound up cutting what remained of bolts 90 degree square on the inboard sides of stringers with a cordless 90 degree grinder to have a surface to hammer on and using an air chisel to first loosen them by hammering away laterally and longitudinally until rust dust began to show, then drove them out toward engines. Once they 'broke' they came out easily. Wear some hearing protection if you experience this joy even if it's just marlboro filters in each ear. This is all easier said than done, it was about three hours for a dozen bolts, including set-up, clean-up, and the obligatory thunderstorm... I’m not complaining, if they’d have just popped out then the stringer would need replacing, LOL!