Mystery needs an Ercoupe Guru...

James, did the annual reveal the possible cause here?

Has anyone ever checked the nose wheel tightness linkage etc.? Part is P factor is the engin still pointing down and to the right? Sounds as if the right wingis not lifting fully I would go thur the rigging of all controls first.

Wow! Thanks for the detailed report!

I really missed the mark when I thought it wasn't an aileron issue, huh? I guess the first step should have been, "with the yoke centered, see if it taxis straight ahead and the ailerons are neutral."

It can be intimidating to hear "not airworthy" from your mechanic but it sounds like all you need is a thorough, proper re-rigging and I bet it'll make a night and day difference. (My coupe restoration had so many "well THAT'S not airworthy" moments that it stopped bothering me too much and I started appreciating the fact that these things can still fly when they're not quite up to snuff, because the former owner has been flying it in that condition anyway)

If you had improper safety wiring in the control system I'm VERY glad you're getting it taken care of. Just in the chain between the two yokes, there are three turnbuckles that need to be wired up right because they control the alignment of the yokes to each other, the yoke alignment to the main control rods, and they hold the chain on!!! That's an absolutely critical safety of flight item. I learned turnbuckle safety wire doing them once, then cutting it off and redoing it to tweak the rigging alignment, and honestly I'll probably do it a third time because my A&P wired my rudder cable turnbuckles and his technique is so much prettier than mine.

Please post again after the rigging job and let me know how it turns out.

Plane finally is in annual.
Despite coming from a self claimed very knowledgeable seller/owner my A&P found a lot of problematic issues with the rigging.
As for the extreme crabbing move right after takeoff we found that nose wheel and ailerons were not aligned. When nose wheel was straight left aileron was up and right was down.
During takeoff roll nose wheel was steering plane straight even with the ailerons were not neutral. But as soon as nose wheel gets off the runway plane is controlled with the ailerons position and naturally sways to the left and ground effect makes the move more extreme for the next 5-10 seconds.

One of the control cables were so tight that exceeded the max allowable tension level and as my A&P described "it felt like a piano string."

All safety wires attached either wrong or some of them were missing where they supposed to be at.
Now, he has the Ercoupe service manuals I provided him and he'll go through and re-rig the whole plane from the beginning.
As in current condition it is not-airworthy he said.
We are still disassembling other parts and pieces. So far engine compression was the only thing came out great and as he said plane was in great shape but the setup was horribly done.
Today and Monday we will go thru wheel bearings, nose wheel, tail height setup, leveling the wings and checking donuts etc...
Fingers crossed!
 

Thank you for the response and the recommendations and especially for you to take time to offer helpful advice. If you were any closer than Maryland I would've fly you here ; )
I have all the Service manuals and documentation that I will provide to the only A&P available in my area. His experience so far is one other Ercoupe he did annual in the past. How long ago it was? No idea! So fingers crossed... waiting that time to come next week.
But I will take a note what you said and check all those items you mentioned. Again, thank you!