Used marine diesel engines with 85 horsepower (hp) have a market value between $9,000 and $12,000, as of 2015. Lower horsepower engines have a lower value. For example, a 25-hp engine can be valued at around $3,000. A non-running engine that requires rebuilding, or engines with under 10-hp, can be worth around $1,000. Powerful engines with over 1,000 hp can be worth between $40,000 and $100,000.
The value of a used marine diesel engine depends upon its age, the number of hours it has been used, its brand and whether it has been used in a commercial or pleasure capacity. The three major marine diesel engine manufacturers are Detroit Diesel, Caterpillar and Cummins. According to professional marine surveyor David Pascoe, these companies make engines of comparable reliability. He suggests that German-brand diesel engines carry a higher price than those made elsewhere. Smaller manufacturer engine brands that fetch higher prices in the used market include Yanmar and Volvo. Buyers who are interested in rebuilding antique boats may value authentic older engines that are in good condition.
The experts at the online magazine Boatingmag.com suggest that a rebuilt engine is worth more than a used engine. This is because a rebuilt engine has been cleaned and repaired, while this is not a guarantee with a used engine. However, they stress the role that salt-water corrosion can play in the overall worth of an engine. For this reason, a reconditioned engine that is under warranty may be of higher value than a rebuilt one.