Motor is a 1993 Johnson 120hp. The timing spec on carb cover says 18degree BTDC,,but I came up with 23,with the boat on land.I pulled all the plugs,all were grounded,,unhooked the throttle cable,held the throttle wide open,and had my dad hit the key.I had a constant 23 degrees,which from what I have read would equate to 27 when the boat is scooting down the lake.I know this motor has been running fine on a houseboat for years,and I have run it 3 times so far on my boat with no problem,,,runs fine,idles fine..Did I do something wrong,,please set me right if I did.