Motor S/N 108912 - I think it is 1988? Started motor with boat on trailer - no problem. Launched boat - motor started no problem. Ran boat for 15 minutes to yacht club to pick up dingy. Shut motor down for 5 minutes. Would not start and hasn't since. Gas is new. Checked for spark and found there was no spark at any cylinder. Not sure what next steps to take. Any direction or assistance gratefully accepted.