Diesel Marine Engine life expectancy before rebuilds?

[JupiterSunsation]

Read an article today on a Viking with a pair of 2400's and now there is even a bigger option out there. Old 300-400 HP non-turbo diesels run tens of thousands of hours albeit in work boat applications rather than weekenders running sportfishes wide open.

Anyone know the rebuild schedule on a new pair of big HP diesels? Some of the diesel forums mention "new throw away" diesels meaning the cost to rebuild a pair of 1000-1400 HP motors can often exceed the value of the motors and many opt to replace the power instead.

On this Viking the option to get them initially was 300K over standard power. But you can have a big sportfish running speeds of almost 50 mph!

[Perlmudder]

big sport fish are badass! always thought they were super cool looking!

[JupiterSunsation]

big sport fish are badass! always thought they were super cool looking!

Tiger just took delivery of a 61 Garlington, he named it Solitude and uses it for fishing/diving. The custom sportfishes are very fast but the production stuff is catching up quickly. The newest/biggest Viking is an 82 with a 22 ft beam and 5000 HP. Boat runs 44 MPH but the fuel burn is ridiculous!

[Chris]

It matters less that it's diesel vs. gas, but more what you're trying to get out of what. a 1000 horse Seatek is going to have a relatively short rebuild interval. A 2400 horse MAN would have rebuild intervals in the thousands. The Seatek is a tiny thing and the MAN is the size of your garage.

[Perlmudder]

The 1500 cats in the boat I am on have thousands upon thousands hour intervals, and that is also mainly due to the fact that if you have to rebuild one, the only way it is getting out of the boat is if you cut a garage door size hole in the side of the boat, so they really try to stay away from having to do that.

[Chris]

There's really no reason to remove large diesel engines. They're fully rebuildable in the boat. You pull the heads, drop the pans, pull the cylinder liners and worse-case, drop the cranks out.

The only reason to pull the engines is to swap in something larger- or more modern.

[DollaBill]

Approx 2-4000 hrs depending on the make and use. While it is possible to rebuild in-boat it is a nightmare compared to having them in the shop. I've done hundreds of these projects. It usually takes more time to prep and clean up than to do the actual job

[Madpoodle]

In the fishing tournaments they big boats used to cry that the center consoles had the speed advantage, and ask for shorter bundaries. Today's sportfish boats have eliminated that little issue..

[HabanaJoe]

My bigger generator sets 500kW (675hp) - 1500kW (2,000hp) are 60 Series DD and big MTU's a couple Cummins as well and smaller sets 100kw - 300kw are all John Deere. They run at 1,800 rpms all day and around 80% loaded - they all go 10,000 hours between rebuilds (some 14,000 hrs). A big boat is very similar to a genset, once on plane you have constant RPM and constant load for long periods of time.

The newer big marine engines should get you 6,000 hrs plus(?)

[TIKI]

How many hours does BobtheBuilder have on his? Aways wondered b/c he does a LOT of boating!

[bluellama]

How many hours does BobtheBuilder have on his? Aways wondered b/c he does a LOT of boating!

When we were with Bob on the FPC Sanibel run, he mentioned that his rebuild interval was 3000 hours. I'm not sure what his hour meter reads right now, but I'd guess between 300-500 hours.....

[JupiterSunsation]

When we were with Bob on the FPC Sanibel run, he mentioned that his rebuild interval was 3000 hours. I'm not sure what his hour meter reads right now, but I'd guess between 300-500 hours.....

WOW that is a big number on the rebuild hours! That would definitely be a reason to build a diesel boat! The diesels don't love high rpms though so if you run it with the throttles mashed into the dash I suspect the rebuild time comes up a lot sooner......

[htrdlncn]

WOW that is a big number on the rebuild hours! That would definitely be a reason to build a diesel boat! The diesels don't love high rpms though so if you run it with the throttles mashed into the dash I suspect the rebuild time comes up a lot sooner......

Most diesels dont run high rpm even mashed to the wall,
in fact thats one of the aspects of diesels that is better than gas engines,
the fact they can run wot for hours on end.

[DollaBill]

And........... there are both 2 and 4 stroke diesels.

[Tommy Gun]

I just had a Cat diesel completely shoot craps in a compressor at 5.16 hours; they have to replace the entire motor with new. Someone forgot to tighten the lower radiator hose clamp and it dumped all the coolant. No low coolant sensor; only a coolant temp senor that never got hot since the coolant dumped so fast. Must have been assembled on a Friday.

[Tommy Gun]

Most diesels dont run high rpm even mashed to the wall,
in fact thats one of the aspects of diesels that is better than gas engines,
the fact they can run wot for hours on end.

I think WOT on my Sea Ray with Cummins 517's is 2,400 rpm.

[gcarter]

Ther're two limiting factors in Diesel engine speed, piston speed and the fact that Diesel cumbustion is slower than gasoline.
The practical upper limit for piston speed, whether gas or Diesel is <3000'/minute. So if your Diesel engine had a 6" stroke you wouldn't want to exceed 3000 RPM very long or very often.
If it were 12", then it would be 1500 RPM, and yes, a 36" stroke engine would be less than 500 RPM.
Of course these numbers are really pushing it.

[Chris]

And it depends on the engine. The Cat 3208's and then the 3126's were medium truck engines. Base power on one was about 220 horse. In the marine versions you got 375 horse. They didn't last long at all.

[BUIZILLA]

I just did some first time fuel and overhaul work on a 3306 CAT with 22,436 original hours.... amazing condition, Texaco URSA Plus 15W40 since new, every 250 hours... pretty impressive

we do ALL of the USCG local CAT fuel pumps and governors.... they expect 10,000, and want 14,000 hours, but they swap out at 6500-7000 due to extended oil service hours... they use... drum roll... Safety Kleen recycled 15W40 oil, MIL PRF 2104G spec

[Bobthebuilder]

How many hours does BobtheBuilder have on his? Aways wondered b/c he does a LOT of boating!

350 hrs now which is probably only 10 % of its life or less. Boat runs as strong as new. If I still had my gas NT I would have had to do another re build or two by now. My fuel consumption is 100% better with 1 MPG instead of .5 MPG with my gas boat. I'm loving the diesel. It is clean and will take me places I could not even think about with the gas boat.

Bob