running diesel engines at slip

[schoonerdog]

Lots of reasons, we haven't move much this season. Basically the boat needs some work that we can't afford yet. At the same time though I want to make sure my engines are being run regularly and in good condition. My engine mechanic suggested running them once a week, for 30 minutes in slow forward against the dock lines. It sounds like good advice. I also heard that running engines at low speeds would tend to glaze the engines (don't really know the correct term). These are yanmar 3JH3E 40Hp engines.

[AnchorageGuy]

Not sure why your mechanic suggested running at slow speed. You might consider a different mechanic. We do run our engines once a week at the dock when we can'[t use the boat much and have done this for years. The first and foremost consideration is "will the dock cleats hold under these conditions. A second line to pilings would be better, but make sure the pilings will hold. You need to get the engine up to temp to accomplish what you want. we run for at least an hour and run our 4JH3E at average cruising RPMs around 2000 to 2500 then boost that to 3500 for several minutes near the end. That is a big stress on dock cleats and lines so extreme care is needed.

[Roy M]

We used to do this when I was doing preventive maintenance programs for my customers. Check your fluids and engine first, warm the engine for a few minutes while you check the dock lines, especialy the spring lines. Put in gear forward at low rpms for a few minutes, then gradually increase the rpms to about half your usual cruising level, leave it there for a bit while inspecting the shaft log, engine vibration, belt tension, etc.. Then reduce to neutral, go in reverse a couple times, then neutral for a couple minutes while rechecking the engine and shaft log, then shut down. Diesels need operation under load, and by varying the rpms you keep the juices flowing, metaphorically speaking.