Looking to acquire a trustworthy Mercury 20 HP 4-stroke outboard? Knowing the current price scope can help you cash. New Mercury 20 HP 4-strokes usually cost between $3,500 and $5,500, depending on options and dealer charges. Secondhand Mercury 20 HP 4-strokes often sell for $2,000 to $4,000, affected by state, hours and general appearance. Note to