Cummins 6BT5.p

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Oct 15, 2009
I am looking at at Trawler with this engine under 1000 hours and 7 years old. I am told by the broker that these are extremely reliable engines which require little maintenance other than fluid and belt changes and valve adjustments. Would appreciate any thoughts on this. Thanks. I am a new user and this is my first post.
The broker is giving you a snow job to make a sale. Yes it is a good engine, but like all diesels it requires regular maintenance. Read the users manual to get a feel for what the normal maintenance requirements are. Then* determine*if the current owner has met these requirements. If the owner has been lax, you will have to fork over several thousand dollars to catch up on the*routine maintenance.
Sunchaser. I do not have access to the manual. Are you suggesting that fluid and belt changes and setting the valves could be several thousand dollars? Are there other maintenance items that require time and money?

Russf-- I think your broker is being somewhat optimistic in his desire to make a sale but I don't believe he is totally out of line. We've had our boat for eleven years, and it was 25 years old when we bought it. As far as the core engines themselves are concerned, all we have done to them in the last eleven years is change the oil and filters, change the belts, change the coolant, and replace the zinc annodes. We've had the valves adjusted once. This is all routine maintenance following the service intervals spelled out in the manual.

But.... stuff wears out or fails and there is no "timetable" for when these things will occur. So over the same eleven years when the core engines needed only routine maintenance as described by your broker, we also had to do the following:

Replace the coolant pump on one engine. Replace flexible impellers in the raw water pumps. Replace the oil and transmission fluid heat exchangers. Replace the exhaust systems aft of the manifolds on both engines. Replace all eight engine mounts. Replace an injection pipe that developed a pinhole leak. Rebuild both alternators. Replace both raw water cooling pumps with new and more reliable pumps (this was a precautionary item, not something done as a result of a failure).

I don't believe Sunchaser is saying that fluid, belt changes, and a valve adjustment will cost several thousand dollars, although at today's labor rates it could come close, but that lax maintenance in the past could mean that other items like heat exhangers, hoses, pumps, etc. may be nearing the end of their service lives and need overhauling or replacement to get you to the point where routine maintenance is all you have to do (for awhile).

As a single data point that might be helpful, the cost to have our local diesel shop change the oil and filters in our engines used to be about $600. This was for two Baldwin oil filters, eight fuel filters of different sizes, six gallons of Delo 400 30wt oil, and the labor. I have been doing our own servicing for many years now so the only dollar cost is for the filters and oil. This is still close to a couple hundred bucks but at least we don't incur a labor rate of close to $100 an hour.
It's not just the maintenance on the engines, it's the entire boat. Now depending on your cruising plans (far offshore or short near-shore jaunts) your tolerance for risk may be different. When I bought my boat, I essentially did every known maintenance known to the engine and other systems, so I had a baseline. Every rubber hose from a seacock was replaced. Every piece of rubber on the engine was replaced. All the heat exchangers were replaced, and the old ones refurbished and tested as spares. The list goes on. With a single engine boat, my tolerance for failure at sea is zero. Much easier to work on the boat in a nice protected slip rather than a storm at sea.

If you want to send me your e-mail address in a private message, I'd be happy to send you my maintenance schedule, which may scare you, but it's compiled from all the systems manuals on my boat, as well as some years of experience. My main engine is a Lehman 135. Single engine owners usually take better care of their engines than twin owners, since a breakdown leaves them drifting!
Thanks Guys. This information has been very helpful. Keith I will take you up on your offer when I get closer to an actual purchase.
Talk to boat owners whenver you can I think you will find a well maintained diesel engine will cause very little trouble, probably less than most other components on a trawler.
My 2003 Monk 36 has that same Cummins engine it has 1680 hours on it I have put 400 of those on since I bought her last November not problem so far. Knock on wood!
Good luck
On the Cummins you have mentioned, the cooling system bolt ons will all need servicing after 7 years and 1000 hours. The Cummins 6bt is very different than a Lehman as far as water pump, HXs and mixing elbow. That is why you need the engine specific manuals.

A thorough engine history, if*believable, will provide the details you need. On the Cummins, the biggest cost item after 7 years will be to service the heat exchangers properly. Go to boat and read the Cummins archives - you will find 1000s of pages of Cummins stories, many related to HXs and failed Sherwood water pumps. They can ship you a manual if you provide the serial #.

Keith is absolutely right about the starting over philosophy, a good engine survey will tell you what you need to know in this regard.
Hard to believe but more engines are KILLED by owners than wear out.

A hard working engine of this style will give 5000 hours and perhaps many more between rebuilds IF it was properly used.

Sitting is really hard on a diesel, as the cylinders may rust .

Most engine builders will have a very specific and detailed procedure for "out of service".

Few owners bother (or even know ) of such requirements , tho there all usually in the Maint (but sometimes NOT the operators book).

Diesels require special oil, and the more modern ones require Diesel Antifreez ,and No car Prestone wont do.

Climb thru the bilge and see what the owner was using for fluids, look for a maint log..

These engines are basically light duty truck engines , which is a great advantage.

They are built for the far lighter loads and ideling a light truck will operate at , so suffer from underloading hassles far less than a genuine medium duty marine engine.

Parts are far cheaper too as there are many aftermarket suppliers for light truck engines.

to the original question about this motor.

The service manual is quite thorough - get one, read it, do what it says.
- hopefully the PO did.

Most folks who have it are happy. The motor being the same block as the one used in Dodge pickup trucks from 1992 on.

Sometime around 1999 or so they played around with adding more valves - the older ones known as the 12 valve motors have a very good record. Though the 24 valve motors seem to have a similarly good rep - both in trucks and boats.

Any motor you put in a boat will suddenly have a new set of issues if not addressed regularly.
I really agree with the previous posts on:
- it is very bad to let a motor rot in place and not use it regularly.
- it is very good to service/maintain your motor regularly.

The motor in my boat is a 1994 vintage - The boat was launched in 1998, so it sat unused for 4 years before it was even started.
I got the boat in 2000 with 230 hours on it - I now have 1700 hours.

This is what I have done:
- oil changes
- coolant tests - one change so far.
- new raw water pump impellors - each season - no missing blades
- new raw water pump 1400 hours - the old one started leaking at the seal.
- std maint & adjustments at service intervals - valves at 1000 hrs etc.
- one new air filter
- I have yet to wear out the belt - but did upgrade the alternator so put a new one on at 1000 hrs.

- I use my boat regularly.

So far, so good - runs like a champ - might run for longer than me -

I typically run no harder than 1700 rpm - which achieves slightly above hull speed for my boat. I need about 40 hp of the 210 available to accomplish this.

If fuel burn is the measurment of longevity as opposed to hours, the motor may get 10000 hours

I have a spare raw water pump and a spare exhaust elbow on board + misc engine stuff.

good luck
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