Ski in NC
Technical Guru
The ECU absolutely sets the injection events to the best point in the matrix. It is absolutely possible to optimize parameters for the given engine operating point. Fixed pitch or CPP.
The prop computer and the engine computer would talk to one another and arrive at the best place to take the engine/propeller combination. I don't believe that could be done without actual torque as an input parameter. For one thing torque limits on drive line components would have to be respected.
I'm sorry, but I way disagree with Mr. Zimmerman. He is basically advising that one should have an engine 3 times larger than is necessary. As if one needs a car that must do 210 mph if one wishes to cruise at 70 mph! Preposterous!
If you think about it, a genset often operates near full load for hours at a time and if well maintained, 12 to 15 thousand hours is not an unreasonable figure for a genset's lifespan. Our Onan passed 19,000 hours and was still running well, though maintenance was becoming a problem with things like freeze plugs and other cooling system parts failing.
Diesels love to be run at their rated continuous operating speed with the correct load. Its all about matching the boat's hull shape and weight, the prop, the trans reduction ratio, and engine hp correctly to get the maximum performance and longevity out of any marine engine. The worst thing one can do is just assume that the former owners propped the vessel correctly. Overloading at low RPMs will kill an engine faster than anything other than a complete lack of use and maintenance, and the less one uses any engine, the more maintenance it will require.
I've been operating diesel engines for more than 5 decades, from single cylinder air cooled portable ones to a few with single piston displacements larger than the cabin many on here sleep in. Never once ran any of them @ 35%. Heck, on many diesel engines, 35% just barely gets the oil and water circulating correctly.
That million miles average for semi engines translates to around 20,000 hours or around 100 years the way most people use their boats.
Exactly.
Which is why i'm so amused by the constant fascination with engine life on TF.
It's probably the least costly aspect of boat ownership.
I'm asked often, with all the cruising i do, 5,000 hours in 5 years, if i'm planning on rebuilding my engine?
Ha !
At a 1,000 hours a year, 20,000 hours will arrive when i'm 90 years old.
As long as a boat owner has a modicum of understanding how engines work (excessive heat or cold is bad), the engine is the least of their worries.
(snipped...)
Where it becomes really interesting is looking at jet RIB's, both gas and diesel. I might have to do that later, but back to a meeting for now.
Diesels love to be run at their rated continuous operating speed with the correct load. Its all about matching the boat's hull shape and weight, the prop, the trans reduction ratio, and engine hp correctly to get the maximum performance and longevity out of any marine engine. The worst thing one can do is just assume that the former owners propped the vessel correctly. Overloading at low RPMs will kill an engine faster than anything
I'm curious. Has your meeting finished yet?
I am glad to see that my article stimulated some conversation on this subject.
I would like to clarify a couple of points. First, the determination about how hard an engine should be pushed must be based on the rating of your particular engine. Cummins, for example, offers Continuous Duty and High Output ratings (along with others in between). Continuous Duty means they designed it to run at full power nearly all the time (commercial push boats for example).
The High Output rating is what almost all recreational boats have. Cummins specifies a power factor of 10-30% for these engines. Those who have a recreational rated engine and who push that engine at power factors of, say, 50-70% will experience shorter time between overhauls.
Second, I emphasized in the article that it is equally important for those who do run at light loads, to periodically run their engines up to WOT or to 80% load. The article included more detail about that protocol.
I hope these comments are helpful.
Steve Zimmerman
, but in any case, his reasoning for using a C rated engine was that since it would be operated at around 25 - 40% load factor, the C rating was fine. I do take it up to EGTs of around 775 degrees every few hours to heat everything up. The C rating has the following parameters: load factor <70%, annual hours <3,000, max power per day < 1 hour.
Surely that one hour per day, sucking like the proverbial, negates any fuel savings gained over the several hours previously by running slow?
I own a 2003 Chevy Duramax with 290,000 miles that runs the same as when new. By-pass filtration since new. No rust to boot.You are my new hero. That you keep the vehicles so long is amazing in this current throw-away society.
Gordon
Synthetic oils allow for extended drain intervals so, no, they are not more expensive. Plus, they minimize, comparatively, the start-up wear. By-pass filtration is quite effective at removing soot particles down to 1 micron as opposed to standard filters at 30 microns. Not magic, just science.There have been a few comments here about the key to long engine life being keeping the oil clean with aftermarket bypass filters, Gulf Coasts, centrifugal polishers, etc.
However I've always thought that just running the engine properly, monitoring EGT and sticking to the manufacturer's recommended oil change intervals should be good enough, without having to resort to expensive aftermarket items or synthetic oils.
Is there really some magic to these aftermarket items?
Getting back to Ford Lehmans, a 35% load (65% of rated RPM of 2,500 RPM) yields about 1,650 RPM. I think most Lehman owners run their engines between 1,600 and 1,750 RPM, perhaps 1,800 on occasion when necessary.Good point BK. Interestingly, Steve Z's PM article states 80% load is around 90% rated RPM. He must have been peeking at a JD sheet. On most marine engines, 35% load is 60 - 70% rated RPM.
Regarding pre-failure analysis (or better said repair it before it breaks) it is commonly done for tens of thousands of variable use engines under extended warranty programs. Especially during the last few decades as on engine diagnostics are downloaded during routine maintenance and oil sampling.
Surely that one hour per day, sucking like the proverbial, negates any fuel savings gained over the several hours previously by running slow?
Synthetic oils allow for extended drain intervals so, no, they are not more expensive.
Delfin wrote;
“My question is, how many actual physical differences are there between engines of the same manufacture and model, but different ratings, or are they primarily how the engine is governed? If the latter, then isn't rating somewhat unimportant in a full displacement vessel since whatever the rating, the engine will likely be run at less than 40% load?”
I see the perfectly powered (loaded) engine in a FD rec trawler as about 60 or so percent. Mine is 50% and I know I could do easily w less power. But it depends on who or what rates the engine. My Mitsubishi is a generic industrial engine. And Westerbeke and Vetus both claim more power .. 44 and 42hp.