Diesel engine questions

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JeffR

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Looked at a boat a couple weeks ago with Cummins 6cta 8.3 (2005) motors. This would be my first diesel.

I know this is basic stuff for many of you, but I'd rather risk asking some silly questions now, than have major issues later.

These are Cummins Diamond Series motors, so they are painted white. I noticed the turbos are discoloring to an off-white/tan color, and there are other small bits that are actually brown. These are obviously results of heat. I know turbos, exhaust, etc create heat, but is this typical, or indicative of a problem?

The second thing I noticed is that there were "diapers" under both motors, essentially covering the entire bilge floor. The boat wasn't what I'd call pristine, otherwise it would be easy to just chalk it up as a concientious owner, but instead I'm questioning whether he's dealing with issues. It did appear that general maintenance was kept up (filters all dated with changes, etc), and the diapers weren't soaked with oil or anything. The broker says that it's pretty common to see this in diesel engine rooms. A line of crap, or reality?

It's typical around here to perform oil changes, etc before going into storage for the winter. Assuming that happened, is an oil analysis a waste of money with fresh oil in the motors? I've been told to have a blow-by test performed to account for that. Again, good idea?

Finally, any general feedback on the Cummins 6cta 8.3 450hp/480hp engines?

This was just a first once-over visit and I will definitely do a sea trial and have a full survey with diesel tech before any purchase, but want to be a comfortable I undertand what I'm seeing before ever getting to that point.

Thank you!
 
1. I had Cummins 450 C's in my last boat with over 1300 hrs and their great engines, one of the best made in its rating range.

2. Turbo' run very hot and it common for the paint on them to be discolored, brown and/or flaking off.

3. I also have oil pads under my Mains & Tran's/V-drives to eyeball any leaks

4. You should have the engines surveyed which would include a see trial after which you can take the oil for analysis the $35-$40 is money well spent
 
I'm just learning about Ford 7.3 diesel for my 'new' van. Turns out they're not all that different than gassers. Gotta learn turbo technology, fuel inj etc. etc. but what the hey.

A bilge liner is a great idea. It'll tell you some history if it looks like it's been in there for a while. Just like new oil, won't tell you much. Get maintenance history, sounds like the PO was consientious.
 
Some discoloration is normal due to heat

Diapers under the engines is a sign that the owner cared about catching stuff early

Oil analysis after change is a waste, even after a couple a sea trial it will only reveal serious issues not more subtle ones
 
You want to get a diesel engine survey. It will cost you about 700 bucks and it is WELL WORTH IT! Saved my butt once and I thought I knew diesels! A good survey will include manometer readings underway to check crankcase pressure for bypassing gasses, a coolant and oil analysis of the engine and transmissions (with appropriate time on the lubricants as Pascal notes). A pressure analysis of the heat exchangers.
 
what Andy and Greg said. Those are great engines, simple and inexpensive, for diesels, to work on. Rated rpm is 2600 and they should exceed that. An oil sample, after some running hours, doesn’t guarantee healthy engines but a bad sample guarantees something wrong. You don’t say how old but if five years or more they need after cooler cleaning. The raw water pumps are a weak spot but nothing you cant deal with.
 
I have the 450C's in my present boat and am very happy with them. I changed out the water pumps, cleaned the aftercoolers and heat exchangers. They have about 650 hrs on them and run strong.

I had a cummins dealership do the survey, they even did a "boroscope" of the cylinders to see if there was any scarring. It cost about $700. They found the engines to be in very good condition, with "minor" work ($6000) needed. I negotiated with the seller and got him to pay 1/2.

I found a place on line where I get Fleetguard filters very cheap.
 
These engines are the marinized version of the mechanical Cummins C8.3 which I have in my "land yacht" (motorhome).

The on road version of these engines today is an electronically controlled 24 valve engine. The marinized engine appears to be a mechanical 12 valve engine that is still produced today for off-road applications and was used in trucks, motorhomes and bus applications until the electronic version was introduced in late 1998.

These are 750,000 mile engines on the road before re-build and generally considered to be "bullet proof". I do not know of any problems assocated with the engine itself. Simplicity and reliability go hand in hand. I read on one forum that a C8.3 was running in an oil field application for 5 years with no problems. They only shut it down for fluid and filter changes!

The turbo-charger for the land version is not painted. Due to extremely high temperatures I would think that discoloration on the Diamond series would be expected.

Clean fuel and an unrestricted air supply is really all they need to give you many hours of service. There is a coolant filter that provides SCA (Supplemental Coolant Additives) required due to their wet sleeve design. This prevents cavitation in the wet sleeve itself. Any engine survey should include SCA levels as there is a range that must be maintained to prevent damage that can result from the cavitation.

Filters are available from Fleetguard (Cummins Filtration Business Unit) and they thrive on Shell Rotella T 15-40W which is available even at Walmart due to its popularity in diesel applications. You can get the oil and coolant filters from any heavy truck shop or authorized Cummins service center

My Cummins does not leak,seep or burn oil and I would expect that from a well looked after Diamond Series.

Hope this helps!

DaveS
 
Simple first step diesel tests
They should start from dead cold in an instant, run smooth and settle into smooth idle quickly, no excuses.
Little or no smoke at cold.
Exceed rated wot rpm at warm idle
Little or no smoke at low load or cruise load
Maintain stable operating temp at cruise and brief wot with clan bottom and props.
Hit or better yet exceed rated wot at full throttle
No leaks of anything anywhere.
No rust
Most of this can be done at the dock at no expense.
If all that is ok then spend money on more detailed inspection but other than previously mentioned stuff they will probably be OK.
 
Bruce,
These are very common motors in Searays .They smoke like hell on start up... Smoke like hell when put under load. They HATE THE COLD.

Other then that there bullet proof. Mechanical diesel thats doesnt smoke and smell ??? I dont think there is one . Electronic totally different animal.

Rob
 
Rob: have to disagree. sea rays are often over propped but those are not smokers unless something is wrong even in the searay I know.
If yours look like the mosquito spray truck something is wrong.
 
We have run 450's for the past 9 yrs, with great results. I haven't had any problems with them, and they don't smoke. Reg. oil and filter changes, and put new impellers 2 yrs. ago. My yurbos are a slight darker rhan tthe rest of the engines.
I use pads each for any leaks that should occur.
 
My take is somewhat the same as above. SMoke on startup from cold is not uncommon but it should clear in a few minutes. Yes the turbos may be discolored from heat and I agree on the diapers. More of an indication that the owner is on top of things than an indication of a problem.

Engine survey is a must.
 
If they smoke when cold your air heaters may not be working. Easy to test.

smoke usually means they are runnimng too cold or getting too much fuel or not enough air.
 
I the diapers had fluids on them I would be more concerned than clean one's that could just be a sign of an owner on top of maintenance.
Bill
 
I use diapers to keep the bilge clean and to easily spot problems.
 
Thanks for all the input, I really appreciate it. It sounds like no big red flags so far, just make sure all the upfront homework is done.

I noticed everyone mentions the 450's, but nothing about the 480's. I understand they're essentially the same motor (same block, etc). We've looked at a couple boats that are pretty much identical other than the 450 vs. 480, and minor differences in options, etc, of course.
 
See if they have the original raw water pumps on them or the upgraded pumps.

And you should check over at boatdiesel dot com
 
quote:
Originally posted by JeffR

Thanks for all the input, I really appreciate it. It sounds like no big red flags so far, just make sure all the upfront homework is done.

I noticed everyone mentions the 450's, but nothing about the 480's. I understand they're essentially the same motor (same block, etc). We've looked at a couple boats that are pretty much identical other than the 450 vs. 480, and minor differences in options, etc, of course.

Click to expand...
I would say that most if not all comments made for the 450 applies to the 480
 
I think the 480s are electronic vs the mechanical control of the 450s. If the block is 8.3 ltr then yes it is the same original block but with upgrades and changes for new technology. Electronic is said to offer smoother quieter running with better fuel control for better efficiency and even less smoke.
 
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