Engine thump

[scotto]

i recently bought a 2003 seaswirl striper with a 2002 90hp johnson outboard . Right away i noticed a slight thump in the motor every 20 seconds or so. Doesn't happen when trolling or when throttle is wide open but every speed in between. Already tried plugs. Could i be trimming it wrong? Warranty for 3 more weeks but must drive about 3 hours to dealer.

[boats.net]

If it feels like it's jumping out of gear, checvk gearcase oil for metal in oil(around drain screw magnet) and check shift cable adjustment.