CAT 3116’s
Capt. Punch -
The 3116 are very good engines provided they are not overloaded and maintained properly, something that applies to all marine diesels.
The Short Version:
Sea trialing while fully loaded, they should hit at least 2800 WOT as verified with a photo tach. Anything less, they’re over propped/overloaded and could develop problems. Again, that’s true for any marine diesel.
The Long(er) Version:
Most of the web’s horror stories about the 3116 relate to large planing hulls. Sea Ray put them in many 42’s, overpropped, and failures resulted. Based on all my research, the French blocks affected a very small batch of 3126’s, never the 3116.
I agree with the recommendation to have the aftercoolers checked - they ingest crankcase vapors and can foul over time, especially if the required single-weight oil isn’t used. But I don’t necessarily agree that, regardless of hours, aftercoolers should be replaced every 8 year’s. Mine has been cleaned and pressure tested regularly and is holding up just fine. The 3116 aftercooler is cooled with antifreeze, unlike the later 3126 which uses raw water to deal with the added heat load from the higher hp rating at 420, so it doesn’t suffer from corrosion issues.
Rather, the typical weak spot is the wet exhaust riser which traps sea water inside it. Over time, pin holes can develop on the inside and, if it does, sea water leaks down into the turbo. The original risers were stainless steel. Later ones cast bronze which can be identified by the pencil zinc in the side. The permanent solution is a custom dry riser with a thermal blanket.
Otherwise, they are fuel efficient, clean burning, and except for the fuel rack/injector timing, can be serviced by your average mechanically-inclined owner/operator.