Cummins diesels
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Ski in NC
Technical Guru
Cummins has made lots of different engines, some are gems and some not so much. Especially in the 80's. They were transitioning from one style (VT series) to the newer style (B and C series). The VT ones are now obsolete and hard to get parts for, the early B and C series had some bugs, but are still can be good machines. The later B and C (say starting in mid 90's) they got most of the bugs out.
Post exactly what engines are in there.
Post exactly what engines are in there.
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6BTA 5.9 600 with 2100 hours. It's an 88 sun deck 42 Jefferson.
firehoser75
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Check out sbmar.com. Admittedly it is a site for a business that sells engines, parts, and service, but Tony Athens, the owner, provides tons of free info and help. He is acknowledged as a Cummins expert.
There are a couple of things I would say to check out thoroughly before purchase. The aftercoolers on these engines need regular, proper servicing (even Cummins does not service them properly if you want the longest life possible) using Tony's protocols from his site. If there are no records stating they have been serviced very recently, factor in new aftercoolers in your purchase price. Also, most early 6BTA's have Cummins exhaust elbows that are double jacketed with the raw water injected near the turbo. Pull off the elbow and look at the turbo. The elbow may have been giving the turbo a diet of saltwater and this would be bad! If that elbow is present, at the minimum plan on replacing it very soon with a custom elbow so that the water is injected below the "breakover point". Much info on Tony's site on all of this.
Good luck in your purchase decision.
There are a couple of things I would say to check out thoroughly before purchase. The aftercoolers on these engines need regular, proper servicing (even Cummins does not service them properly if you want the longest life possible) using Tony's protocols from his site. If there are no records stating they have been serviced very recently, factor in new aftercoolers in your purchase price. Also, most early 6BTA's have Cummins exhaust elbows that are double jacketed with the raw water injected near the turbo. Pull off the elbow and look at the turbo. The elbow may have been giving the turbo a diet of saltwater and this would be bad! If that elbow is present, at the minimum plan on replacing it very soon with a custom elbow so that the water is injected below the "breakover point". Much info on Tony's site on all of this.
Good luck in your purchase decision.
wwestman
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Do the maintenance that the book calls for. These engines are what is in Dodge pickups and lots of over the road trucks. Same basic block. Easy to find parts. Easy to find someone to work on them, at least in the areas I have been in. And if, heavens forbid, you destroy one, Cummins remanufactured motors are available.
Marlinmike
Guru
You got very good advise from all the above posts, I would only add get a cummin's mechanic to do the engine survey, I know some surveyors say they do both I like having a specialist.
firehoser75
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One more comment. There is another Nordic Tug owner that I know who has well over 9,000 hours on his 2001 6BTA and it is still running like a top. He goes from Seattle to Alaska every year.
Ski in NC
Technical Guru
The 300hp 6BTA in the late 80's may have the old style heads with 9mm injector holes, and welded aftercooler. These engines did not hold up if run hard (like sportfish boats). Did fine in trawler service where they ran mostly easy. Many were upgraded to 7mm heads and the modern type aftercooler, then they held up as well as any.
Parts are very available, though some old stuff might need to be upgraded to new stuff, usually a good thing there. Prices generally lower than other brand engines, though still will sting depending on what you need. Run of the mill parts reasonable.
Post photos of the engines if you can.
Parts are very available, though some old stuff might need to be upgraded to new stuff, usually a good thing there. Prices generally lower than other brand engines, though still will sting depending on what you need. Run of the mill parts reasonable.
Post photos of the engines if you can.
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Lots of good info on the 6BTAs already posted. I'll add one more thing. The positioning of the front motor mount makes the raw water pump's impeller a little hard to get to. If the factory pump is installed, you often have to loosen the front motor mount and jack up the front of the engine about 1/4" to be able to get decent access. Some people have changed to an aftermarket water pump, Sherwood I think, that makes it easier. Other people have creatively modified impeller puller to make the job easier. Not a deal-breaker, by any means. Just something to be aware of.
John
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The original pump is Sherwood. Much better aftermarket pump is Seamax from Seaboard Marine. First thing I did on our NT 37 with Cummins 6BTA 5.9 M3 330hp was replace that Sherwood pump with the Seamax.
https://www.sbmar.com/product/smx-1730-seawater-pump/
https://www.sbmar.com/product/smx-1730-seawater-pump/
Cummins, in general, have a very solid reputation. Their use as marine propulsion is just one small part of their overall use, from trucks to being the leading selling marine generator. Also, they have a good reputation for service and standing behind their product. I look at how they stood up to help DHayes. First class.
firehoser75
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Chuse927,
From your photo, those are definitely the "stock" exhaust elbows I was talking about. You will need new "custom" exhaust elbows ASAP, plus you need to check the exhaust side of the turbo for saltwater damage. In a worst case, the engines could have been on a saltwater diet with the turbo shot and maybe even damage into the engine! Definitely get that checked out as in the worst case scenario it could be very expensive!
From that photo I can't tell which Aftercooler they have.
From your photo, those are definitely the "stock" exhaust elbows I was talking about. You will need new "custom" exhaust elbows ASAP, plus you need to check the exhaust side of the turbo for saltwater damage. In a worst case, the engines could have been on a saltwater diet with the turbo shot and maybe even damage into the engine! Definitely get that checked out as in the worst case scenario it could be very expensive!
From that photo I can't tell which Aftercooler they have.
Ski in NC
Technical Guru
No fan of that mixer either, but at least the one visible has a decent down-angle on it so should drain ok. The ones that drain usually live. But we are talking 30yrs!!
Aftercooler "looks" like the modern one. A pic of inboard side of stbd would tell for sure.
Aftercooler "looks" like the modern one. A pic of inboard side of stbd would tell for sure.
Jon H
Senior Member
We get 20,000 to 22,000 hours out of our KTA / QSC 38's.
Admittedly these are big engines but have proven very robust.
Aside from basic maintenance, injectors around 10,00 hours and
heat exchanger plate cleaning annually.
Note - this is in GoM where summer water temps can reach 90 F.,
in cooler H2O this is probably not a concern.
Admittedly these are big engines but have proven very robust.
Aside from basic maintenance, injectors around 10,00 hours and
heat exchanger plate cleaning annually.
Note - this is in GoM where summer water temps can reach 90 F.,
in cooler H2O this is probably not a concern.
Fletcher500
Guru
The usual caveats, how was it’s past life, PM’s done, etc.
The Navy refits their swift boats in the San Diego area for the regular Navy, and Special Ops with Cummins. Mostly QSB’s. Granted, it’s not the engine you are referring to, but a close relative. It shows the kind of trust they have in the package because a mechanical can literally mean life or death for the areas some of these guys operate in.
The Navy refits their swift boats in the San Diego area for the regular Navy, and Special Ops with Cummins. Mostly QSB’s. Granted, it’s not the engine you are referring to, but a close relative. It shows the kind of trust they have in the package because a mechanical can literally mean life or death for the areas some of these guys operate in.
ben2go
Guru
The 5.9L Cummins is used in a lot of commercial boats in power rating from 180hp-315hp. Converted non marine engines can go from 80hp-450hp. I'm planning on a 180hp variant set up for keel cooling and dry stack exhaust. Of course I haven't built my boat yet so that may change to the 4 cylinder 3.9L version of the 5.9L.
I'm fighting town haul for permits for my building shed. Was supposed to start Thanksgiving week on my boat.
I'm fighting town haul for permits for my building shed. Was supposed to start Thanksgiving week on my boat.
BruceK
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I recently saw a twin Cummins engined boat, where the port engine exhaust exited the engine, then swept upwards 90 degrees,then turning to pass across/over the engine towards the hull where it made a 90 deg. left and began to drop down, at which point the raw water entered,continuing down towards the muffler etc. Looked weird.
Comodave
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It probably would not have a problem with water backing up through the exhaust...
T210DRVR
Senior Member
I like the older mechanical 5.9’s. Several Sport Fishing operations in Baja used the 250 HP variants in the 90’s and they liked them a lot. They were pretty fuel efficient and they got good life out of the engines. IIRC, they ran them pretty conservatively about 1800 - 2000 RPM. Parts are readily available and fairly reasonably priced.
Boatingbill
Veteran Member
I’m not really thrilled with the 300hp rating. These engines were made for 200-250hp. Higher hp=less life. That being said they are great engines. Marinized variations can vary depending on as others have mentioned exhaust. Get them checked out. If they check good I wouldn’t worry about them to much. Btw you can get the hp reduced pretty cheaply. If the engines have the parts ie crank, rods, and pistons to be set at 300 would pick up a lot of life hours at 250, or even 275. Keep in mind that could require a prop change. If not planning on spinning them up in the very high 2k range you will be fine. I’d shoot for a hull speed rpm around 1,500-1,600 cruising around 2,000 wouldn’t take wot passed 2,500
