Hi, I have a seagull boomerang and have an os.46ax mounted on it. today at the field the spinner came off along with the prop. So I opened and put the back (plastic piece) of the spinner and the prop on the engine but by mistake placed the prop incorrectly, now when I am trying to remove the prop it is not coming out because the engine is rotating, what should i do please help
What I have tried till now :
Placed a plier with cloth and then tried to unwind the plastic but somehow the engine screw moves along

I have placed a pic for reference of the problem

Thanks Divay

Try to rotate the prop with a chicken stick (A small blow to release the jam)
You dont have to screw the spinner bottom and prop in to the shaft. it can be slipped in without any play. Try to hit the propeller with a small wooden stick or chicken stick

Many options are available.

1. Open back plate and use a crank lock tool.

2. Insert something soft like tooth brush handle through exhaust port to block the piston.

3. From what I read, you just have the prop on, not the nut. If you can get another nut, put both of them on and tighten them against each other (not on the prop). Hold the outer nut with the spanner and you should be able to lock the crank shaft and rotate the prop.

Just flood (overflow) the engine with the fuel (Piston will lock)  

Avoid to open the rc engine....  

Open the plug, pour in fuel and close it ?

No, Through the carburetor. pour fuel in carb full then rotate prop anti-clockwice then refill carb
Do this process till engine jam. U can take the fuel out through plug hole.

But i never take out the plug for take the fuel out through plug hole. There is another process.
Engine is flood- invert the fuselage nose slightly leaning down about 20-25*. Rotate prop clockwise if engine jams then rotate half-half both clockwise & anti-clockwise about 10-15 times some fuel comes out through carb then rotate the fuselage to muffler side & nose 20-25* up in same position (Knife edge Position). Do this procedure 2-3 times, your engine will drain fuel through carb & muffler.

Avoid to open the rc engine....any part unnecessarily 

I was *partly* kidding about filling the engine through the plug, although that is one quick way of doing it, without having to remove the muffler to insert toothbrush handle etc (and then worry about the RTV/gasket etc while connecting the muffler back).

It is for heli pilots that the trick of removing excess fuel via the muffler itself is of great help.  It is pretty hard to rotate heli engines by hand once they are flooded, so the simple trick is to tilt the heli so that the muffler side is downwards, and just spin the engine with the starter, it drains the excess fuel out in no time.  Otherwise it is a tough job trying to manually rotate the fan, clutch etc in the confined space inside most heli frames.

That is a good one!

I did the same thing on a Saito FA82.  I didn't ream the prop before mounting and I couldn't get back off.  I tried everything and ended up using Dremmel tool to remove (Be careful NOT to bump the shaft and ruin the threads).  I got it off carefully and successfully.

Hope that helps

hEY .... SORRY I guess I never thanked for the help... the situation stands resolved.... I used a cloth to hold the engine and then turned the prop and removed the same....

Once again thank you to all for the help

If you get into similar situation another trick is similar to the toothbrush method advised by Rajesh. I do not recommend flodding method as too much force on a flooded engine could result in broken con rods.
Use a piece of flat stout wood,  insert from the exhaust over the piston and now when the prop is rotated the piston would lock and on continuing to rotate the prop it would rotate without the crank itself rotating.
This method is also very useful for removing a stuck clyinder in the crank case