The difference between a dirt diesel and a marine diesel is seawater, the heat exchanger and most specifically the seawater mixing elbow. Run a Diesel engine with a restricted heat exchanger or carbon plugged exhaust and it will not live a long and prosperous life. You will see this in boats brought out of the charter trades where despite regular maintenance schedules, and oil changes the engines have obviously been popped by heat. Every Yanmar owners manual I have ever read talks about blipping the throttle to rated max RPM after a session of prolonged idle to “remove carbon deposits”. They are designed as extreme duty high speed diesels. But every marine diesel lives under imminent threats of overheat that dirt diesels do not - noted in the first sentence above.
All diesels run a risk of overheating due to lack of maintenance dirt or marine. The key with any engine is that it is
well maintained. Again, I will gladly pony up for the clean well maintained (with proof / service records) 3000+ hour marine diesel vs. the slopy ill maintained low hour engine every day of the week. I think far too many folks are overly concered about mileage/hours on motors when the real concerns should be about how has it been maintained. For example our engine gets:
Oil changed twice per year (Rotella 15W-40 since new)
Gear lube changed every oil change
Magnet for gear oil drain plug
Gear lube cooler was added (not stock)
Has a remote oil filter that added 1 quart of capacity to the system and over 4X the filtration media
Engine coolant is changed every season with Rotella ELC.
When ever an engine part gets some rust or corrosion it is removed, bead blasted & re-painted
Hoses inspected continually and replaced when ever needed
Every hose clamp on the engine is non-perforated
HX anode replaced twice yearly
Air filter replaced bi-yearly
Impeller replaced each year
HX pressure tested bi-annually
Valve lash checked / adjusted every 300 hours
Injectors dropped at injector shop and tested /serviced every 500 hours.
When the engine is run it is always allowed to run up to full temp before it is shut down
The engine has a full gauge package (not the standard factory set up) not just idiot lights
The fuel tank is 100% spotless and features an on-board fuel polishing system that keeps it that way
We only run ValvTect fuel and only fill up at ValvTect dealers only (this is pretty easy to do in Maine)
I fully expect this engine to outlast us and I would take this 4000+ hour engine every day of the week over most sub 500 hour engines. If an owner even did half of this list I would have little concern over an engine with high hours. Maintenace is most important.