As i stated before, your ski is a basket case from what i could see in the pictures, it is very old being from the 70's and you will just have problem after problem if you don't take everything apart and fix it properly. I know this because we have a 78 440 that is still having problems with anything that is still stock. get yourself a good shop manual and it will be a start in the right direction. your spark issue could be water in the ebox or a bad stator both have been an issue on the 78.