I have a Mariner 25hp Year ? Serial # 6611310, on a 14ft Alum Boat, Run?s Great at mid and top end Speed is 30mph on GPS, I can take it out run it at 20-30 mph for 10-20 miles a day and it runs great.But will not Idle at low speed,will Shake and Stall out,I put new Spark Plug, new gas,new Gas Tank, compression test 110lb in Both Cylinders,I Would Appreciate any HELP Please