Hello!
I have been having trouble with my Mercruiser 120hp. It starts great from cold, then won't start from warm / hot.
I took the flame arrestor off and turned the engine over. To my surprise (and horror!), after about two turns of the engine, petrol poured out of the pipe circled in the image below like it was coming out of a hosepipe and onto the hot manifold (obviously the flame arrestor had been catching it). The reason the engine wouldn't start from warm / hot is because (I deduce) that the petrol is filling the carb and flooding it.
My diagnosis is that the float needs adjusted to cut off the fuel flow when necessary. It's an easy job to do and I'll tackle it in the coming days.
Is my diagnosis fair - or have I got the function of the red circled pipe in the picture wrong? I'm sure it is an overflow pipe for cases such as this one.
Help or confirmation of my diagnosis would be gratefully received!
Thanks,
Ian.

Yes, you are correct about the over flow pipe, open the carb up and have a look inside, may need a rebuild kit.

Check that the float is actually floating properly. I got a tiny leak in the copper float, allowing fuel inside, which then didn't cut off the supply.

All sorted! I got a carb "repair kit" from the USA which included all gaskets, new float, springs, choke device etc. I srtripped the carb and re-built it; all working great now. It was a float problem - I don't know whether or not it had a hole in it (none visible), but the fuel cuts off fine now and the engine is (currently!) running great.
Thanks all.