update. Looking through the exhaust port, the piston goes up and down (I knew it did) and the ring looks ok for the small section I can see through the port but....

when I put my thumb over the spark plug hole and turn it over there is very little pushing and sucking on my thumb but it does do some. Now for comparison, I went over to my Ryobi in the same condition and turned it over and there was much more pressure on my thumb. When using light pressure it would actually blow air past my thumb. The Mac would not do that with the same pressure.

So, there is not enough compression in the Mac. Piston/ring problem?

Can I just put that crank in the other Mac that I have? Is it a lot of trouble or difficult? Will I need any special tools like a press or anything? My other mac is not threaded for the prop nut.

Thanks.

Rob