6CTA 8.3 480HP

[john plachtyna]

I am trying to understand some basics about a 2004 6CTA 8.3 480HP engine.

I currently have a Yanmar powered boat and am familiar with the issues of propping at WOT, Diesel Maintanence and Exhaust Design.

I am looking at a 2004 Tiara with these engines. Is this engine a 480CE or am I confusing this?
Is this an electronic engine to achieve this HP?
Are there any issues to be aware of with this engine besides maintenance, proper propping and exhaust design?

Thanks for any help

Topic

[john plachtyna]

Steve,

Thanks again for your insight. I appreciate your efforts in responding.

The 38′ Tiara’s I have been interested in are around 2005 so there will be no warranty recourse. I’m glad it worked out for you. My tolerance isn’t going to be too high for dealing with a major engine rebuild if these engines have been “abused” so I am trying to learn all the potential pitfalls before committing to these boats.

Your points to evaluate make this much clearer.

John

[Rob Schepis]

Nice post Steve, keep them coming, your contributions are spot on and greatly appreciated.

[Steve Lewis]

Personal Opinions

JP,

I can not be certain but the QSC500 started showing up in Sea Ray boats that were manufactured in late 2005 and early 2006. Notably the 44 Sundancer. Not sure when Tiara started using them. I would choose a QSC 500+ over a 480CE if I had the choice. That is my personal opinion though so take that for what it is.

As for the discoloration, Yes the heat generated by the Turbo compressing the air causes heat. That heat inturn will discolor the paint on the turbo, the piping that leads to the AC and the AC. It is not really burning it, it is just discoloration from prolonged exposure to high heat. Baking it is more how I think of it. That high heat is generated by demanding high horsepower from the engine. Over propping makes that condition worse. So I have adopted my own personal scale for determining acceptable discoloration. It is pretty simple so again, take it for what it is. My own opinion.

Pudding. Vanilla, Butterscotch and Chocolate. I think we are all somewhat familiar with those colors so as long as those parts are within the Vanilla to Butterscotch range I find that acceptable as long as those colors are accompanied by reasonable engine hours. The lighter the color and the higher the engine hours the better. The darker the color and the lower the engine hours means bad things are in the future unless dealt with properly. Especially on the 480CE. IT all comes down to Fuel burn at RPM. If you like the boat and the engines show signs of being treated nicely then you might consider that boat even if it has the 480CE. THere are plenty of people on the forum with the 480CE. If you find one that has not been abused badly and fix the root cause by tuning the props then you may find a Tiara that gives you years of boating enjoyment.

It all comes down to your ability to tolerate things. My wife and I bought a boat back late 2017 that has known fuel system issues and we went ahead and bought it anyway because maint records showed that some of the remediation work had been completed. This season we experienced the severe end of those problems anyway, but to Mercury Marine’s credit they have stepped up and are taking care of us even though the boat is well beyond any engine warranty period. We like our boat very much and have enjoyed cruising it on our own and with friends. I was “Not Happy” at the time we experienced the issues but in the end we will have a boat that is properly sussed and ready to do a lot of cruising next year. Mackinac Island here we come!!

Long story short, you can find a boat that you like and deal with the engines and other systems to get it a known good condition and then go boating. Choose well based on your tolerance for dealing with things.

Our ultimate goal is a Diesel powered boat that my wife and I can cruise with another couple in comfort and maybe even a little style. So I have been actively reading and contributing on the forum as a way to learn. We will find one eventually and then set about getting it properly setup for our longer term goals of the Great Loop.

Happy Boat Hunting!

2 users thanked author for this post.

Graham Smith, Tony Athens

[john plachtyna]

Steve,

Thanks for all the info. I had actually read those articles before and that’s what prompted me to ask about these engines. I have re read them again!

The boats that I am looking at are Tiara 38′ opens. It seems as those built around 2004,05 have these 6CTA 8.3 engines at 480HP

I have seen the Aftercooler picture in the mentioned article with a “burned” outside appearance. Is this due to the high exhaust temps in an over propped boat that the cooler can’t cool down?

Would you know when the QSC series engines started to be manufactured? Would it potentially be better to look at these boats with this newer series?

Thanks, John

[Steve Lewis]

It probably is a 480CE

JP,

Odds are you are looking at a 480CE. Tony has mentioned in quite a few posts over the years that this engine is a “Hybrid” Mechanical/Electronic engine. Sort of a transition design between the 6CTA xxx line and the QSC. Which model boat are you looking at? The 3800 Open? 4000 Express? Totally Curious…….

The 480CE engine has a well known “Design Flaw”. Give these a good read.

The Cummins 6CTA 8.3 Marine Engine Story

Propping the Cummins 6CTA 8.3 480CE vs. 430/450 Diamond Engine

In summary – Cummins took a perfectly good 450 Diamond, added electronics and dialed up the fuel burn without enhancing the internal parts to handle the extra heat and stress generated by the extra fuel burn. That lead to some spectacular failings depending on the prop load.

Post some pictures of the engine compartment and specifically the Turbos and Aftercoolers. While you are at it, take a good picture of both of the data tags so that the sbmar crew can run the serial numbers and tell you 100% what you are looking at. The discoloration of the Turbos and Aftercoolers will give you an indication of how hard these engines have been run and whether you should “turn and run”.

If you like that boat, then take her out on a sea trail and record the fuel burn numbers. Ignore the load numbers and focus on the fuel burn numbers. That is the important data element. Record the fuel burn numbers from 2000 – wot and then compare them to the chart that is in the 450 vs. 480 article. At that point you will see how the engine is loaded, over propp’d vs. under propp’d. I can pretty much tell you that it will be over propp’d unless the current or previous owners knew what they were doing in this regard.

The degree of over propping, the amount of hours in the over propped state will be very instructive on the health of the engines.

Let us know……..

[Author]

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