If the engine was properly laid up, 3 years storage should be no problem. A number of times my Ranger 33 has sat for at least 2 years and it's Atomic 4 has always started up when I put it in the water again. It should have been fogged or had oil added to the cylinders prior to storage. But even if it didn't, in my opinion, odds are it is in roughly the same condition now as it was when it was stored unless it was stored in a very damp environment.

The biggest question is why it was removed from a boat. People rarely remove perfectly good engines from boats unless they were underpowered to start with or are switching from gas to diesel. I'd want to talk to the guy who pulled the engine.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13