Cummins 6CTA8.3-M Heads

[Curt Schultz]

I’m looking at purchasing a boat that has a pair of Cummins 6CTA8.3-M engines, CPL# 2960. At the very least I would follow the advice that is given here about propping the boat to the 450 fuel curve. My question is in regards to the heads. The engine SN’s are 46435824 and 46434682. Are these engines heads subject to the valve seat dropping out that I’ve been reading about or are they of a later vintage that I don’t need to be concerned? I’m planning on doing the great loop next year and don’t want to be rebuilding motors mid loop. BTW, if it matters, engines have about 800 hours on them. TIA

Topic

[Richard Dodson]

Hi, My ESN is below the TSB that Cummins issued in 2006 but above yours, you probably have the old heads.  The upgraded head # is: 4942463.  I had the misfortune of dropping an exhaust valve, around $22,000 to rebuild it. As a precaution, I swapped the head on the other side, around  $9,000. In addition I reduced the prop pitch 2″. This resulted in the desired 450 fuel burn to be 27.4 GPH at 2200 RPM which results in 18-19 Knots.   The seat failed around 1400 hours.  There are several articles under “Tony’s Tips” that address the issue.  You also need to be mindful of the aftercooler servicing and the techniques recommended by SBMAR.  My boat is a 2005 SeaRay 390 MY, what’s yours?  You might post your RPMs vs. Fuel Flow every 200 RPM beginning with 1800 and some pictures that show the color of your aftercooler and turbo pipes.    

[Steve Lewis]

CS,

Welcome to the family.  I am a fellow 480CE owner.  There is a Cummins Technical Bulletin that states that ESN# 46634956 or higher have the upgraded valve seat material so yours are below that and require some attention.

Give the forum a search and use my name as Author and you can see what we did with ours.  We are based in Marblehead OH and have cruised extensively around the Great Lakes since we had our heads replaced and are in good shape.  I would want my boat fully  sorted before I start the Loop.  I would also want to have a substantial spare parts bin so that I am only looking for help as opposed to parts in remote places.

What make, model and year boat do you have?  Post pics of the engine, turbo and exhaust area so that we can see the general situation and make recommendations.  It took us 2-3 years to get everything done that we needed in order to feel comfortable cruising distances with confidence.

Let us know if you have further questions.

[Author]

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