800 hours.
Yanmar SB-8 (ca. 1977) used year round in salt water. I change the engine oil much more often than suggested (cheapest form of prevention), replace the entire diesel oil fuel content in my tank, the water separator, fuel filter, engine zinc, impeller, and water hoses every Spring regardless of actual engine usage during the previous year. I flush the system with Salt Away if I will be leaving the boat unattended for a while. (I am currently replacing the mixing elbow after 7 years and having the carbon deposits in the exhaust manifold sand-blasted away). Engine starts first time every time, and runs like the proverbial Swiss watch in any sea state.