Marine Engines

bandlow1

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Dec 8, 2012
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I am sure that I will get lots of differing opinions but I am interested to know which diesel engines are considered to be most reliable, require the least maintenance and are economical to operate? Also and maybe more important which engines should be avoided? I am also interested to know if fuel consumption has gone down significantly over the past say 10 to 15 years for a given engine size. For example does a 370 hp from 2000 burn significantly more fuel than a new 370 hp engine.

One last thing. Are there issues with buying a boat with an engine that is say 25 years old with relatively low hours if it has been well maintained?

I know I am asking for a lot of info.

Thanks for your thoughts on these issues.

Happy New Year!
 

djmarchand

Captain
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Jul 24, 2012
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Litchfield, CT / Punta Gorda, Fl
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Atlas Pompano 23 outboard
One factor that affects maintenance and reliablility is turbocharged, seawater intercooled engines. These require rigorous maintenance of the intercooler (air cooler) or catastrophe can result.

And if you are talking about the 370 hp range, all will be turbocharged and seawater intercooled at that hp rating.

As an example of fuel economy, a good legacy engine at that rating is the Cummins 6B 370 hp. Its modern equivalent is the QSB 380. The newer engine will burn 5-10% less fuel and will smoke less and be quieter.

I doubt if you will find a compact 25 year old engine at that hp rating. Most will be big and heavy.

At that rating you have several choices; the Cummins, a Yanmar 6LY, a Volvo D6 and a John Deere 6068. The Cummins and JD are generally considered as the strongest.

David
 

BillD

Admiral
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Sep 1, 2011
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Portsmouth NH, boating out of the mighty Merrimack
Boat Make
25 Terry Jason with Cummins 370 power
I am sure that I will get lots of differing opinions but I am interested to know which diesel engines are considered to be most reliable, require the least maintenance and are economical to operate? Also and maybe more important which engines should be avoided? I am also interested to know if fuel consumption has gone down significantly over the past say 10 to 15 years for a given engine size. For example does a 370 hp from 2000 burn significantly more fuel than a new 370 hp engine.

One last thing. Are there issues with buying a boat with an engine that is say 25 years old with relatively low hours if it has been well maintained?

I know I am asking for a lot of info.

Thanks for your thoughts on these issues.

Happy New Year!

David is spot on with his post.

I'll add this. Let's take the Cummins 6BTA 370. There are over 3 million "base engines" in world wide service across all industries. A marine 6B base engine will last a good solid 6,000 hrs. in marine service before it gets a bit "tired". The engine can be rebuilt.

I'll also add that the vast majority of ALL marine service engines will NEVER see the total number of service hours the base engine was designed for.

Why?? Here's a list of reasons in no particular order:

Marine age, no different than us humans aging !
Rust and corrosion from salt water drippings,spray immersions
Multiple owners who are clueless
Lack of rountine maintenance, NO not talking oil changes and filters,
lack of maintaining the salt water cooling side of the engine.
Weekly due diligence of the engine, checking ALL over.
Overheats, no alarms
Overloading the engine, no understanding of propping
Overloading the engine X 2
Broken serpentine belt, no alarm
Worn broken hose, no alarm
No alarms
No alarms X 2 :D
The "nut" behind the wheel:rolleyes:
Failed alternator bearing, NO alarms.
Worn/busted raw water pump, NO alarms
Poorly designed exhaust system...BIG culprit !
Bad luck!:confused:
I may have missed a few reasons!

Think about it. An average recreational season may be 125-150 hrs. of engine use. Multiply X 20 years, maybe 2500-3000 TOTAL hours.
Toss in 3 or 4 owners who start out "clueless" as owners.

What are the odds of the base engine reaching 6,000 hrs. ???:(

FWIW,


Bill D
 

petrel

Rear Admiral
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Dec 17, 2011
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NC
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56' DMR, 31' BHM
The engines in my 1996 DMR (Performance Marine) pre-date the boat. Johnson Towers 671 TI's from the 80's. We did major overhauls at about 15,000 hours. Not bad for some running take-outs that Dwight Raymond put in a spec boat. But they were run regularly and they were mostly run easy, several hundred rpm's off the top. But they do burn some fuel compared to a modern diesel. Fortunately the boat pushes easy, so it's been worth keeping them a while. Repowering can cost a LOT of money, and it can take many years to get it back on the fuel savings.
 
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