Hello, i acquired a used moki 2.1 in excellent shape. Engine is probably 3 years old.
Can anyone tell me what the thread type is, i mean pitch and size etc? I need a new
nut so i can hold on the prop. Thanks....

Just take the motor with you and go down to the local Ace hardware or other nuts-n-bolts store. Buy a grade 8 nut. I think it's 10mm, but it's been a long time since I ran the big Moki engines.