Well, finally some small update on the renovation!

I have managed to draw all liners, but it was not a straight forward task. To make room for the power jacks I first removed as many BSF 1" pins as possible using a 2m bar. I guess I manged with some 35 out of the total 48. Then I used two 10t power jacks on top in addition to two 5t porta power against the crankshaft. Even so it was on the edge the liners popped with a bang. Amazing that nothing broke, considering the force must have been in excess of 50t in total. The tool I used was a 20mm steel plate under the liners and a M30 rod to the top where it connected to a 100x100x10 tube above the power jacks. Have attached a photo, but rather dark I'm afraid. With the liners removed, it was a piece of cake to warm up the pin holder from the inside, and so I tremoved the rest of them! Next I cleaned out the water cavity (very messy, must have been some 10kg of rust there) and painted with a special urethane heavy zinc paint. After some more cleaning up of the heavy soot oil in the sump, I will put in three new liners I managed to find together with three of the best used ones. For the purpose I made an indicator clock to measure the wear.

Yes, I also managed to find O-rings of the exact size near by. They had both metric and imperial, so it was a simple task. I also made a drawing of the head gaskets. It took some iterations with printing and cutting cardboard for testing before I was satisfied. Then I found a local supplier which was actually cheaper then Gasketstogo (inc freight, toll and VAT that is).

All in all, most things are now disassembled but I need to clean out the engine base, which is a messy thing. The old lube is like tar and full of soot. After that I will level the engine and start assemble it. However, now summer is here and outdoor work on the boat is prioritized so I will probably wait until fall to continue on the engine.

Hi again and thank you all for the replies!

Yes cobbadog, I realize that I should have told more on the background and my plans, my bad!

I reside in Gothenburg, at the west coast of Sweden. As it is a coastal city, we have some old ships and henche ship engines near by. Most of them are Swedish or at least Scandinavian, like NOHAB Polar, Skandia, Seffle or B&W Alpha. The Lister Blackstone is quite rare. I am a member of a non-profit association for historical commercial ships, i.e. over 12m. Mine is 25m and considered medium sized. It is privately owned and renovated by me, which is on the edge but only works since I refurbish old equipment and try to learn along the way. I've attached a photo of the boat in the floating dock this summer when I did a overhaul with sandblasting and repainting.

The head gaskets are roughly 44x35cm, as the attached picture. The one installed are simply hand made, which can be seen on the uneven shapes, and made from a single piece of dense gasket material. The protruding liner is also clearly visible. I asked my local gasket provider, rima.se, and they kind of recommended Flexitallic RGS3, which is a steel reinforced carbon gasket. However, since they did not have any experience in combustion engines, they could not tell for sure that it would work. After talking to the manufacturer, Flexitallic, I found they did not know either. Guess they are more into chemical/process industry. Thing is I would not want to blow out this gasket, and if I could learn something about proper head gaskets and their compression rates at the same time it would be even better.

My original plan was to provide my gasket provider with a drawing, like dwg, and have them machine out the shape from a suitable material. They have a large sized gasket CNC knife cutting machine. This will be rater expensive including all the several m2 of gasket material as I would want 12 pcs, double my inital demand for the 6 cyl engine. 38ac and mobile_bob, you both recommended Gaskets To Go, that is gasketstogo.com in Thailand, right? They look really professional and I will definately ask for a quotation, but I think the total, inc trp and import charges, will be hefty. Even so, you have a point in getting the professional stuff, and there is only half zombie apocalypse here for the moment!

As for the gasket thickness, the manual list a liner projection of 0.23-0.35mm, so let's say 0.3mm. As an example, let's go for the RGS3, which has a max compression rate of 50%, which will then occur around the liner. Using a 2mm gasket, we then get the head to block distance 0.5*2+0.3=1.3mm, which corresponds to 35% compression. A 3mm gasket gives 40%. etc. Is this a useful way to deal with gaskets to make sure they do not leak or am I way off? 

Regarding the o-rings, since the cylinder dia is 8"3/4, or 222mm, the rings are around 240mm, which is too large for my present provider. Bringing the liner is possible, but not feasable since it is not easy to carry along. I use cranes and fork lifts not to kill myself while handling things. I'll see if I can find another company for the o-rings.