QSB 5.9 vs. 480CE

[Rob McLaughlin]

I am new to the site and new to big diesels, though I have been messing about in boats for a long time. Considering purchasing a 2004-07 Sea Ray, and looking at 390DA or 420DA. The 420 is equipped with the notorious 480CE, and I have read a lot about it’s propensity to drop valves. I have also read Tony’s article on propping the boat like a 450C, but I’m still getting the feeling that the engine is a bit fragile.

The 390 Sea Rays from that era are equipped with the QSB 5.9. I have been looking around, and have not seen major issues being discussed with that engine. Are there known weak spots to look out for on the QSB? Is there a clear advantage to the QSB over the 480CE, or am I just tripping over some bad press?

Of course the Admiral likes the bigger boat, but I want to be careful about what I’m getting into.

Love the site – appreciate any advice.

-Rob

Topic

[Tony Athens]

Thanks Tom……………………..You did do it all right and it all showed up in the end..

Tony

[Rob Schepis]

Great info here. As we all know, all of these higher HP/Liter diesels can be “fragile” to things like over-propping, marine age and the nut behind the wheel. Treat ’em right and they return the favor. I think the “take-way” of this thread thus far is to keep your options open and judge the boat as a whole (or hole as the saying goes…) And, MOST importantly, keep the admiral happy!

[Tom Bartolomei]

I owned a 2005 390DA with QSB 5.9 380’s for some time. I did much (proactively) surrounding the maintenance of them following the guidance and expertise residing with Tony and the folks in Seaboard. Great engines all around. At the top of the list, I ended up re-propping my 390. Went from stock 4 blade props of 21″ x 23″ down to 21″ x 21.5″ and then to 20.5″ on the pitch. That was about as good as I could dial things in. Just sold the boat 3 months ago, 1000+ hours. 3060 RPM’s WOT @ 94% engine load. Full fuel, 4 adults, 300 lbs dingy on the swim platform.

Aftercooler maintenance is easy when done the right way and at the right frequency. Access in the 390DA ER is decent. The exhaust set up is logical and my turbos never had a dose of salt, ever. I did replace the stock walker airsep system with the Envirovent system, much better. To remove and plug the oil return on the port engine was probably the hardest ‘access’ related effort I faced on the 390. New alternators, and new SMX pumps , and new belts along the way. She fetched the highest price on the NA continent 3 months ago and is/was worth every penny.

Tom

1 user thanked author for this post.

Corey Schmidt

[Joel Hilden]

I have a 2005 Sea Ray 390 Motor Yacht with the 480 CEs. There is nothing fragile about them; they’re basically a CTA 450 Diamond with an electronic governor. As Tony has stated many times, the problems generally come from overpropping. However, the earliest 480 CEs had a cylinder head that was more prone to problems, so Cummins superseded it with two new part numbers. Mine has the 2nd Gen heads, according to the Cummins guys who performed the engine survey.

Newer versions of my boat (40 Motor Yacht) were equipped with the QSB 425, which probably saves over 1,000 lbs in weight and gives the boat similar performance. However, you’re pushing more power from each liter of displacement, which can present the problems that Tony has outlined in the past when it comes to long-term durability.

[Author]

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