Managed to get the engine mounts undone, and all the bolts around the bell housing, pried the bell housing open a few inches all the way round then over the next few hours got a more decent gap but it just pulls back to the original spot , the gear lever pulls back and forwards as I try pulling it apart,
I assume there is a rusted bearing or something, I don't care if anything gets destroyed I just want it out.
am getting worried I am going to wreck the seal and start filling up with water.
i would love to pull the whole thing out in one go but the space in there is ridiculous so doing it in stages as I get deeper in.
can't even find room to get a grinder in there to cut the shaft..
any ideas on getting it apart ? Thanks.

In the absence of someone who knows about your engine, see if you can get an exploded diagram of that part of the engine. You might be able to figure out whats stuck or if something else needs unscrewing. This one of gearbox came from DAM Marine.

Hi Mag
When I removed my YS gear box it was a matter of undoing the bell housing bolts and pulling it back.
Maybe a few taps with a hammer to get it moving.
I can't imagine anything rusted together inside (unless she has been under water).

RE, it just pulls back to the original spot , the gear lever pulls back and forwards as I try pulling it apart,

This sounds like it is in gear or the gear selector is somehow jammed.
Try to remove the gear selector lever and internal assembly.

Garu