1989 Yamaha 115 HP/ model 115ETLF Hard start, poor idle, dies upon acceleration. Then runs like a top above

1500 rpm to WOT. Ran fine last summer,was winterized, has fresh fuel,always have used fuel stabilizer, fresh NGK B8HS-10 Plugs,fresh oil,Plugs are not wet

Have good spark at all plugs, will rev up fine when not in gear,however, under load hesitates or stalls, not smoking any more than normal, what do I need to check for this problem? Thanks