The owners manual of my 2008 Yamaha 25hp 2-stroke motor says to torque the drain and fill plugs to 6.6 foot pounds. I don't have a torque wrench and I don't have a clue what 6.6 foot pounds feels like. Do I need to go buy a torque wrench to get it right? I'm scared of both not tightening it enough or tightening it too much. Is hand-tight enough?