Cummins 480 CE 6CTA. White smoke and knocking

[JJM]

Hey guys need some input. Think I have an idea what’s up but would like to bounce it off Tony and the other guys. So today driving home cruising one motor starts stumbling a bit , I start backing down to check what’s up and it stumbled right Down and shut off before I was able to. I changed Racor filter and re primed and after a lot of repriming finally got it to re fire. Motor now runs but has a top end knock and is pushing white smoke.I’m leaking towards the idea it is a stuck injector. But not 100%. Is surely hope it’s not the motor . Stuck going back on one motor

Topic

[Paul Gois]

Bad Cummins heads… what a nasty surprise.

Hi Richard, I am also undergoing the same dilema right now… My mechanic was able to drop the oil pan in place and the engine did not have to be moved so we got lucky there. I had gathered some #’s previous to knowing any of this, and I was burning 27gph at 2160rpm. Seems really close but slightly over. Since I was not tracking the gph for this purpose, I have #’s such as 18.5gph at 1870 rpm. Same exact engine same exact way that happened to you… It’s amazing to me that with so many of these cases out there, that Cummins has not stepped up.
I am having my port side head removed and inspected (replaced of course as well) as this
has been such a let down to what I thought was a superb engine and company. We will be putting mine
back together in a few weeks and can’t wait for the warmer weather to get here to get the testing done
so we can enjoy our short summer seasons up here in the NE. Keep us informed on your progress and I will as well.

1 user thanked author for this post.

JJM

[JJM]

Richard Dodson wrote:

I have a 2005 Sea Ray 390 MY, 6CTA 8.3 480. about 1300 hours. While running, starboard engine began running rough. Limped home on port eng. Found oil quantity had increased a bit. Pulled valve cover, #4 cylinder rocker shaft broken. Replaced, engine ran on all cylinders, however knocking was heard on top, in the vicinity of #4. After removing the head, it appears that the #4 exhaust valve seat failed. Best guess is that the knocking and rocker arm shaft failure was a result of the piston forcing the valve seat material against the head and valves. Looking at a 30K rebuild, head, pistons, sleeves and bearings. All will be done without pulling engine.

The engine# is: 46451379. I think there were more than one generation heads, the replacement part number that I have is 3936155. Am I correct, as the last thing I want is to have an old head with defective seats.

A year ago, I had the props refurbished to the 450 fuel curve, at 2100 RPM the smartcraft is indicating 26 GPH (total). WOT is 2600 with full fuel, water and 4 adults. Of course I have no idea how previous owners operated the

boat.

Any comments or suggestions would be appreciated.

Sorry to hear this Richard. Sounds all too familiar. I feel your pain. I am still working through mine. Unfortunately you had the old generation heads that are prone to failure unless propped down to the 450 Diamond curve although I have still heard of them failing when not over propped. Your WOT on smart craft though should have been 2680 rpms and if propped to the 450 curve should be about 27.2 at 2200rpms. So your 26 gph at 2100 sounds pretty close to spec. I am attaching the bulletin for you that will show you the new generation head numbers.

I am surprised you say will be repaired without removing engine? The engine will need to be unbolted and hoisted up high enough to drop the oil pan. Is this what you mean? Keep us informed how you make out. Thanks for sharing your info.

[Tony Athens]

480CE valve / seat drop

What was your GPH at 2000, 2100, 2200 RPM, loaded for bear after your reprop?

Tony

[Richard Dodson]

I had the same occurrence

I have a 2005 Sea Ray 390 MY, 6CTA 8.3 480. about 1300 hours. While running, starboard engine began running rough. Limped home on port eng. Found oil quantity had increased a bit. Pulled valve cover, #4 cylinder rocker shaft broken. Replaced, engine ran on all cylinders, however knocking was heard on top, in the vicinity of #4. After removing the head, it appears that the #4 exhaust valve seat failed. Best guess is that the knocking and rocker arm shaft failure was a result of the piston forcing the valve seat material against the head and valves. Looking at a 30K rebuild, head, pistons, sleeves and bearings. All will be done without pulling engine.

The engine# is: 46451379. I think there were more than one generation heads, the replacement part number that I have is 3936155. Am I correct, as the last thing I want is to have an old head with defective seats.
A year ago, I had the props refurbished to the 450 fuel curve, at 2100 RPM the smartcraft is indicating 26 GPH (total). WOT is 2600 with full fuel, water and 4 adults. Of course I have no idea how previous owners operated the

boat.

Any comments or suggestions would be appreciated.

[chuck young]

I would bet ours is the same. I have previously posted photos of my exhaust from the turbos and beyond about a month ago in this forum and have also discussed the system with Justin via phone and email. My mechanic and I visualy inspected the elbows and turbos while apart for the head changeout and found them to “look” good. Justin and I agreed likely ok to take another look late next season. Boat is wrapped and tucked away at a marina. I’ll attach couple photos here I previously posted.

1 user thanked author for this post.

JJM

[Tony Athens]

I’d e posting good pics ASAP so we can all “see” what my be going on…

[JJM]

Chuck I was checking out the exhaust on a 390 MY the other day and see that there is water injection both right at the turbo and then right before it exits the boat at the exhaust muffler . You will see if you loom further down. I believe its going through the turbo and then making its final exit at the muffler. See if you can take photos of the whole exhaust. I know its tight in there!

[chuck young]

Dan thanks, thats what I referenced ( been talking with Justin at Seaboard) as an aside in my previous post. Also had forum discussion about this on a previous thread about a month ago. It seems some manufacturer designers have their heads up their own exhausts.

[Dan]

Chuck,
You may want to look into the way the exhaust is set up on your boat

Marine Exhaust Risers that are Doomed to Fail

[Rob Schepis]

chuck young wrote:

Correction…. I meant Justin not Jason…sorry

I corrected your prior post accordingly.

[chuck young]

Correction…. I meant Justin not Jason…sorry

[chuck young]

Tony / Corey this is the best pic I have of the SV right now. Boat is on the hard now. The manual only indicates its SC5000, version 3.xx. Engines: EIN 46408683 and 46409102. I would think I could possibly install exhaust water temp sensors in the elbows to analog guages??? Elbow pic below. Side note…Ive been discussing these elbows with Justin as to future modification. Right now they and the turbos look good.

[Tony Athens]

This is a Corey Question.. He should jump in here..

In the mean time, post a really good pic of your display and a engine serial number.

Tony

[chuck young]

I have the System View Smartcrap on the 05 390 MY and cant read boost on it. Do you have some type of gateway readout, a different monitoring system or were you making an educated guess “19-20?” Wish I could read boost and especially exhaust temp. Was able to read those on my last 06 Sundancer with 5.9s and VesselView.

[JJM]

All 450 fuel curve spec.

13.5 GPH 2100 rpm

Boost 18-20?

[Tony Athens]

Cruise RPM = ??

GPH at that RPM = ??

Boost at Cruise RPM =

Tony

[JJM]

Tony Athens wrote:

My thoughts are above, although a really good shop may work too..

I believe hardened valve seats are shrunk fit in place , not pressed in.

Tony

Tony what do you suggest as a safe, sustainable EGT when cruising and at WOT?

[JJM]

Tony Athens wrote:

My thoughts are above, although a really good shop may work too..

I believe hardened valve seats are shrunk fit in place , not pressed in.

Tony

ok

I have always seen them pressed in on other engines I have built. I have heard they can freeze them with nitrogen to make it easier but still pressed in. Ill have to dig back in again to see how its done today.

[Tony Athens]

My thoughts are above, although a really good shop may work too..

I believe hardened valve seats are shrunk fit in place , not pressed in.

Tony

[JJM]

Tony Athens wrote:

This is just an IMO………………..

Yes, use a good independent mechanic to do the all the labor end on the project.

But personally I’d buy new/exchange Genuine Complete heads from Cummins–Now you have a real guarantee that your head is right–No inspection needed and all will be new and built to their highest /latest standards.

Curious–How does one inspect a valve seat as to whether the next time you come off plane fast the the seat cools before the head around it cools, and it then drops?

I suspect Cummins has changed this spec as to how the seats are installed in the marine heads for this motor to help this operating condition that occurs in marine use.

Tony

Tony what are your thoughts of sending the original heads to a machine shop and having them clean, test and press new seats and install new valves on them? I am concerned if Cummins didn’t get it right the first time who’s to know if this will happen again……?

[Author]

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