iMac G3 Slot loading - Unable to Boot OS8 or OS9. OSX Works

[Roman78]

I own a good looking iMac G3 Slot loading Blue Berry. 350 Mhz G3. I tried to install OS 9 without any success. I can boot from the Install CD and i am able to install to the Harddisk, but after that it won't boot from the harddisk. It is stuck at a white screen.

So I swapped harddisk from another G3 whit a Working installation, resulting in the same behaviour. On the original Harddisk is OSX installed and that is working. When i change the Startupdisk in den Controlpannel it wont boot any more. I than have to boot from a OS9 CD and change the Startupdisk back to the OSX installation to boot again.

So does not matter what i do, i cannot install OS9. So i tried original OS8 cd delivered whit the iMac. Same result: I can install it but cant boot from it. Changed harddisk several times.

Could it be something whit the Firmware? What could I do?