Mercury tracker pro series 115hp won’t start

[Motocody23]

Ran fine past 2 summers, now it’ll crank for a few seconds and then lock up. Let it sit a bit and then go try again and the same thing. I haven’t gotten to look at it much so what’s a few things to look at?

 

[mechanicman]

Sounds like a timing issue still do the basics. Compression test. Spark test. Fuel sample.