Looking to purchase a trustworthy Mercury 20 HP 4-stroke engine? Knowing the current price range can save you cash. New Mercury 20 HP 4-strokes generally cost between $3,500 and $5,500, subject to options and dealer charges. Secondhand Mercury 20 HP 4-strokes often go for $2,000 to $4,000, affected by shape, usage and general appearance. Keep in mi