Official Cummins 6cta 450C thread

When I broke my factory turbo to manifold seal it was to have the turbo rebuilt. Part of that was honing the mating surface on the turbo. I reinstalled it with a new gasket without rtv and it leaked slightly when on plane. So I took it off and cleaned manifold side really well, put in new mounting studs and new gasket with rtv. That worked. Just sharing an experience you might find something useful in.

Next step is to remove turbo and remove the exhaust elbow (studs rusted into turbo). The 10mm bolt heads are super easy to strip and will be replaced with 13mm head bolts. I will get the mating surface on the turbo redone. Need to inspect turbo for any cracks. Last step will be remove the exhaust manifold and have it resurfaced. Might be worth doing the exhaust manifold now as the admiral is getting pretty pissed. Keeps telling me to hire a Cummins mechanic....not yet!
 
Can someone confirm that the 6CTA takes 3-E-2 anodes? One for the HE and 2 for each after cooler?

Thanks,
Bennett
 
Thanks guys! I am sure I will come with more questions. After having the QSC 500s, looking forward to the mechanical engines. I have been running the Performance Metals Navalloy anodes for about 5 years with excellent success.

Thanks again!
Bennett
 
Next step is to remove turbo and remove the exhaust elbow (studs rusted into turbo). The 10mm bolt heads are super easy to strip and will be replaced with 13mm head bolts. I will get the mating surface on the turbo redone. Need to inspect turbo for any cracks. Last step will be remove the exhaust manifold and have it resurfaced. Might be worth doing the exhaust manifold now as the admiral is getting pretty pissed. Keeps telling me to hire a Cummins mechanic....not yet!
All back together....had both turbo flanges refinished at an automotive machine shop. ($60). Test run is next weekend. Antifreeze in and no leaks when run for 15 minutes at idle.
 
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I did a quick search and not much came up.

I wonder if anyone invested and used the fuel pressure gauges. I'm looking for the following info and was hoping that someone here went that route already:

1. What gauge fits our engines to test fuel pressure coming from the lift pump (low pressure side)?

2. What gauge fits to test high pressure pump side?

3. Does anyone have fuel flow ratings for the lift pump and the fuel flow ratings for the high pressure injection pump?
 
By the time someone answers, I hope to already have found it. But where is the f@#$ing primer button on this engine? Specifically the port engine but for the next guy wondering, where are they on both?

When replacing the on engine fuel filter, everyone (here and on Google) says to fill the filter and prime the engine using the button. But I’ll be damned if I can find it. Everything I push is the head of a bolt. Ugh. Pictures would be fantastic. Thx.
 
Ok, so here’s the real issue. Went out yesterday for a trip. Could not get the port engine up past 2100 RPM, even at full throttle. SB engine came up fine. Absolutely no smoke from the engine. Seemed to run fine otherwise. Several attempts with the throttle to lower RPM and raise it achieved no difference. Switched Racors while on the water, but no change. Limped back home. After docking (and shutting off the engines) I restarted the engine and got to full 2800 RPM in neutral. So the engine *can* get higher. It just wasn’t. Fired the engine up again this morning and I can still get it to 2800 RPM at max throttle, unloaded. FWIW, I can get to 3000 RPM on the SB engine, unloaded.

After coolers were taken off and cleaned this year. Air filters were cleaned a few weeks ago. Bottom was cleaned about a month ago. Racors were replaced in December. But again, I swapped to a clean one while on the water yesterday, so that one should be new (0 hours). Engines have about 50 or so hours since Racors were replaced. Also, just checked and to my novice eyes there don’t appear to be any air leaks in the lines from the filters to the engine.

Lack of power and no smoke seems to indicate a fuel flow issue or an excess of air. But like I said, I swapped Racors on that side. And don’t see any air leaks. Should I just start swapping fuel filters - Racors and on-engine?
 
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Look at the turbo hoses. Since the after coolers were removed one probably popped off.
 
Look at the turbo hoses. Since the after coolers were removed one probably popped off.

I did a more thorough inspection of all the hoses from both airseps through the aftercoolers. They are on solid. I reseated the main air filter, too. No issues there. The fact that I can get to 2800 RPM unloaded but can’t get to running RPM loaded is indicating (to me, anyway) that this isn’t an engine issue after all. I’m thinking now it could be a fouled prop, bent shaft or perhaps a cutlass bearing. Trying to schedule a diver ASAP to rule out fouling.

Oh, and as I guessed, I found the fuel prime buttons. They look like large white top hats. The SB one is right there in your face. Once you find that one, locating the port one by reaching over the engine from above is relatively easy. I’ll post a pic next time
 
I did a more thorough inspection of all the hoses from both airseps through the aftercoolers. They are on solid. I reseated the main air filter, too. No issues there. The fact that I can get to 2800 RPM unloaded but can’t get to running RPM loaded is indicating (to me, anyway) that this isn’t an engine issue after all. I’m thinking now it could be a fouled prop, bent shaft or perhaps a cutlass bearing. Trying to schedule a diver ASAP to rule out fouling.

Oh, and as I guessed, I found the fuel prime buttons. They look like large white top hats. The SB one is right there in your face. Once you find that one, locating the port one by reaching over the engine from above is relatively easy. I’ll post a pic next time
Alex F posted just before you, because he is having similar problem. He started a thread on sbmar. Maybe follow along with it and as well:

https://www.sbmar.com/community/topic/450c-6cta-loss-of-power-troubleshooting/
 
I did a more thorough inspection of all the hoses from both airseps through the aftercoolers. They are on solid. I reseated the main air filter, too. No issues there. The fact that I can get to 2800 RPM unloaded but can’t get to running RPM loaded is indicating (to me, anyway) that this isn’t an engine issue after all. I’m thinking now it could be a fouled prop, bent shaft or perhaps a cutlass bearing. Trying to schedule a diver ASAP to rule out fouling.

Oh, and as I guessed, I found the fuel prime buttons. They look like large white top hats. The SB one is right there in your face. Once you find that one, locating the port one by reaching over the engine from above is relatively easy. I’ll post a pic next time
I've had fouled props, an out of spec shaft and a bad cutless bearing and none of them would cause that restriction. They'd just shake the boat to some degree while the rpms climbed. I've also been through bound up turbos and clogged air filters on other 400DB boats with Cummins, and they noticeably spit out black smoke. Based on 2800 rpm max high idle and no black smoke, I'd be focusing on fuel delivery to the engine. But that's just me.
 
I've had fouled props, an out of spec shaft and a bad cutless bearing and none of them would cause that restriction. They'd just shake the boat to some degree while the rpms climbed. I've also been through bound up turbos and clogged air filters on other 400DB boats with Cummins, and they noticeably spit out black smoke. Based on 2800 rpm max high idle and no black smoke, I'd be focusing on fuel delivery to the engine. But that's just me.

Thanks. That’s why I’m here: to seek the experience and wisdom of others. I read Alex’ post on Sbar. It is eerily similar. The one difference is that I have no temp issue. My engines are running solidly in the 160-170 range. So things like water flow probably don’t apply in my case.

Don’t take the 2800 RPM as gospel. That’s from the helm teach which may read 100 or more RPM low. I need to get it calibrated with the actual engine RPM.

I see why you’re saying it’s likely a fuel issue. But what do you make of the fact that I can get to high RPM in neutral? The fuel is flowing then, isn’t it?

In my survey in 2019 the surveyor mentioned the port cutlass as a potential repair. It spun, but with noticeably more effort than the SB. I’m wondering if that could be getting worse and causing binding? There is some vibration at idle on the port side. That’s why I’m wondering if maybe it’s not fuel related (not arguing with you, just thinking out loud).

I noticed something else today, too. Doing a spin to rotate into my slip today, I noticed the starboard engine was dominating the spin. That is, with the port in reverse and SB forward instead of just rotating CCW, I was also going forward. Both engines were idling. In backing in, I had to give throttle to the port to help with the rotation. So it didn’t feel like I was getting the normal power from the port, even at idle. One other weird thing, out on the water at 2000 RPM each side, my wake wasn’t symmetrical. The normal white waves came from the Sb side. The port side had its wake too, but they were more like swells than waves. May be nothing but seems to point to an imbalance in thrust between the sides. Which we already know. These things don’t really help me narrow down the issue. But they are interesting.

I think I’m going to get a diver out to rule out prop or shaft fouling or damage. Also, I’ll change the Racor and secondary, just to see. Then I’ll probably have to call in the experts.
 
Thanks. That’s why I’m here: to seek the experience and wisdom of others. I read Alex’ post on Sbar. It is eerily similar. The one difference is that I have no temp issue. My engines are running solidly in the 160-170 range. So things like water flow probably don’t apply in my case.

Don’t take the 2800 RPM as gospel. That’s from the helm teach which may read 100 or more RPM low. I need to get it calibrated with the actual engine RPM.

I see why you’re saying it’s likely a fuel issue. But what do you make of the fact that I can get to high RPM in neutral? The fuel is flowing then, isn’t it?

In my survey in 2019 the surveyor mentioned the port cutlass as a potential repair. It spun, but with noticeably more effort than the SB. I’m wondering if that could be getting worse and causing binding? There is some vibration at idle on the port side. That’s why I’m wondering if maybe it’s not fuel related (not arguing with you, just thinking out loud).

I noticed something else today, too. Doing a spin to rotate into my slip today, I noticed the starboard engine was dominating the spin. That is, with the port in reverse and SB forward instead of just rotating CCW, I was also going forward. Both engines were idling. In backing in, I had to give throttle to the port to help with the rotation. So it didn’t feel like I was getting the normal power from the port, even at idle. One other weird thing, out on the water at 2000 RPM each side, my wake wasn’t symmetrical. The normal white waves came from the Sb side. The port side had its wake too, but they were more like swells than waves. May be nothing but seems to point to an imbalance in thrust between the sides. Which we already know. These things don’t really help me narrow down the issue. But they are interesting.

I think I’m going to get a diver out to rule out prop or shaft fouling or damage. Also, I’ll change the Racor and secondary, just to see. Then I’ll probably have to call in the experts.
Sounds like you have a good plan. One observation about spinning props by hand. I've done that on four different 2001/2002 400DBs with Cummins and ZF-280 gears and everyone was noticeably harder to turn on the port side. A mechanic once told me it's because it's the counter rotating transmission. He didn't elaborate beyond that, and I didn't look into it any further.
 
I agree with Bill. You’re most likely looking at fuel delivery based on what you are saying. You should know how accurate your tachs are, you say they could be off a hundred, could they be off 200? Because high idle should be 3000 +/- 20 rpm’s or so. 2800 isn’t making it.
Things like this are a lot easier to get to the bottom to in person than over the internet. We’ll help best we can but....
Make sure your throttles are advancing all the way to the stops and a little into the spring. Make sure the fuel shutoff solenoids are opening fully. Change the secondary filters on the engine.
Let’s see where we are then. Good luck
 
Sounds like you have a good plan. One observation about spinning props by hand. I've done that on four different 2001/2002 400DBs with Cummins and ZF-280 gears and everyone was noticeably harder to turn on the port side. A mechanic once told me it's because it's the counter rotating transmission. He didn't elaborate beyond that, and I didn't look into it any further.
The port side actually turns the same way as the motor. The engines turn counterclockwise looking at the flywheel.
 
Thanks. That’s why I’m here: to seek the experience and wisdom of others. I read Alex’ post on Sbar. It is eerily similar. The one difference is that I have no temp issue. My engines are running solidly in the 160-170 range. So things like water flow probably don’t apply in my case.

Don’t take the 2800 RPM as gospel. That’s from the helm teach which may read 100 or more RPM low. I need to get it calibrated with the actual engine RPM.

I see why you’re saying it’s likely a fuel issue. But what do you make of the fact that I can get to high RPM in neutral? The fuel is flowing then, isn’t it?

In my survey in 2019 the surveyor mentioned the port cutlass as a potential repair. It spun, but with noticeably more effort than the SB. I’m wondering if that could be getting worse and causing binding? There is some vibration at idle on the port side. That’s why I’m wondering if maybe it’s not fuel related (not arguing with you, just thinking out loud).

I noticed something else today, too. Doing a spin to rotate into my slip today, I noticed the starboard engine was dominating the spin. That is, with the port in reverse and SB forward instead of just rotating CCW, I was also going forward. Both engines were idling. In backing in, I had to give throttle to the port to help with the rotation. So it didn’t feel like I was getting the normal power from the port, even at idle. One other weird thing, out on the water at 2000 RPM each side, my wake wasn’t symmetrical. The normal white waves came from the Sb side. The port side had its wake too, but they were more like swells than waves. May be nothing but seems to point to an imbalance in thrust between the sides. Which we already know. These things don’t really help me narrow down the issue. But they are interesting.

I think I’m going to get a diver out to rule out prop or shaft fouling or damage. Also, I’ll change the Racor and secondary, just to see. Then I’ll probably have to call in the experts.

I'd say that if you don't see your engine get over 2920RPMs at no-load (in neutral) test, don't bother investigating your running gear, as it's irrelevant until no-load WOT is to the specs (2920-3020).
 
The port side actually turns the same way as the motor. The engines turn counterclockwise looking at the flywheel.
Roger that. Mark, does your port prop shaft turn as easily by hand as the starboard?
 

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