I recently purchased a Wilker boat with a 50HP Johnson. A couple of questions: <br /><br />The boat is 1987 but can't confirm year of motor: serial # is ZWL15356J687<br /><br />The motor seems to "chugg" and wants to stall at idle to low throttle - I changed the plugs. Has improved some but not alot. Should I change the wires to be sure. Any other items I should check. (I'm very new to boating).<br /><br />Thanks kindly.