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Old 28-01-2014, 07:20   #16
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Re: Diesel Major Overhaul

Our plan is a live aboard and running up/down the atlantic coast twice a year. Then trips local to GA where we would like to relocate (from CT). None of the motor yachts we looked even have a gas option so I'm actually looking forward to diesels. If I had to replace my engines on the Viking we have now, i would opt for diesels but that is an expensive investment in a 1977 model (so no I wouldn't do it based on her age and the fact that I'm not going to keep her to make it worth my while).

And thank you to everyone who has contributed to this thread. It really does help clarify things for me and provides a wealth of information.

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Old 28-01-2014, 07:58   #17
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Re: Diesel Major Overhaul

I think it was well covered, in short those Detroit diesels listed within a sport fisherman environment when a heavy boat is planning and requiring the use of a lot of horse power it will wear out quicker then the same engine in a trawler using 80hp. So in your plan of traveling the coast slowly it's not that costly given you are barely stressing the engine/s.

Good diesel survey before purchase and then go through the complete cooling system afterwards and you’ll have what you need.

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Old 28-01-2014, 12:26   #18
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Re: Diesel Major Overhaul

Originally Posted by pkrawetzky View Post
Lots of interesting info... Maybe it's my understanding of what MOH really is. It sounds like what everyone is saying is there is your routine maintenance (valve adjustments, Turbos, air coolers, etc) and then there is a complete tear down/rebuild. I guess I looking at that routine maintenance as MOH.

It think the best thing I can do when looking at the engine side of things is get the records (if they exist) and have a thorough engine survey done. That in of itself has several definitions but from what I gather includes compression tests, engine/trans fluid analysis, etc.

Yes, and yes.

We had our last engine survey done by the local Cummins distributor, and after purchase, we moved to a marina with on site certified Cummins tech (even though I do most of the routine annual maintenance myself, now). Helps to have good input from the start, and nearby adult supervision from then on

You can pretty much deal with any brand, that way.

Selby Bay, South River, Chesapeake Bay, USA.
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Old 28-01-2014, 12:59   #19
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Re: Diesel Major Overhaul

Hmm, OK, I know of several large (550hp +) turbo diesels with over 30,000 hours. They are Scania. Low rev, high torque, commercially rated engines. Look for a commercial rating on whatever engine you get. Some engines are rated say 500 HP for leisure, and 350 commercial. Run it at the commercial specs, maintain it, and it will last a long time, perhaps as long as the boat!. Learn to do the basic maint yourself, and you'll get to know the engine. Nothing wrong with a turbo either - look at the trucking industry, but the same goes - maintenance. Good oil of the right specs. Filters all changed on time every time. Run a good air filter (like K&N). Don't baby it when new (glazed bore issue), or even at all. Don't Idle it for long periods - diesels like to work. If it is a turbo model, make sure you run it fast enough to prevent carboning of the turbo.
Finally, my diesel has 9800 hours, still going strong! :-)
Matt Paulin
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Old 18-02-2014, 19:09   #20
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Re: Diesel Major Overhaul

I grew up with Detroits. When I came around they were still Gray Marine. The 671 was the most common. As a kid I worked on the river and most engines were Detroits. Many were WWII built engines. What I like about them is that they are mechanical. No electrical parts except for the starter. The injectors are fired by the cam. Once it's started it will run as long as fuel is available. No circuit boards, no wireing, no expensive computer box. They are rebuildable many times. Most of the accessories and injectors are rebuildable. Parts are available everywhere. Many aftermarket part manufactures keep prices reasonable.
I have 671 mains about to be rebuilt. They have much more than 10,000 hours. Who knows when, if ever they were rebuilt. The blocks are about 60 years old. Other than some smoke, especially at start up, they still run fine.
My boat was built as a patrol boat with a semi planing hull. 83', about 80 tons. The 671s push this boat at 10 knots using 10 gallons an hour at 1800rpm. When I bought the boat it used 14 gal/hr. @ 10 knots. With a little work you can gain some economy if you're not in the upper 20% of horsepower. Detroits run at high rpm don't last as long, but neither do most other engines. There are other fine engines. Many get better economy. But I don't feel any of the engines with electronic controls are reliable. They'd be ok in trucks, but not out to sea.

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