I would say it is a timing issue.----Try another flywheel.----I could simply go to another motor here and try another flywheel.----Or mark your flywheel for TDC.----Use a timing light to see where it is firing !
Put a 12 volt battery negative to the engine block.-----Put 12 volts to green wire.----Prop should turn clockwise with slight drag.-----Lock up turning counter clockwise.----Repeat test for blue wire.----Should be opposite of course.
The ---Wellcraft -----Brochures of those days said ---" World class boats"-------Know of one individual who had to redo transom / stringers on a 79 Scarab Sport.-----Meant to look good in the showroom.------Not really made with quality materials.
Sounds like the classic broken piston rings.-----Remove that cylinder head for inspection.----I believe you will not like what you see in there.----Motor likely needs 4 O/S new pistons / rings.----Will happen to everyone of these motors !
A classic case of " new motor " issues.-----A new battery is cheaper than damaging electrical stuff on new fangled motors.----But wait , is a new EMM even available for these things.----Easier to find / get parts for say an old 9.5 Evinrude
Sorry-----I do not consider that to be a " clean " motor.-----Good luck with it.----Model # is ?----Serial numbers the same on swivel bracket and powerhead?
