Engine wont pass 1320 rpm

[jeff panton]

Hello,

I have a pair of Cummins 6CTA 480 in a 2005 Rampage 38 express. I have never had any issues with them and they run great other than some white smoke at idle. Recently when trying to plane I noticed the starboard engine would not pass 1320rpm whilst the port engine would. Whilst sitting at 1320 rpm I am getting black smoke but the engine just wont go up. I have done the following:

Changed all fuel filters
Checked running gear and bottom to be clean
Checked props for damage, none seen
Removed air cleaner and tried without success
Checked turbo to be spinning free

I am now a little stumped as what to do, I kept pushing the port engine and after a good while it seemed to carry up the starboard engine in RPM and when both were at 2000 I checked the boost and engine with issue was about 3 psi off the other so don’t think boost is an issue. To get the port engine to carry up the rpm on the starboard is quite difficult and takes quite a few trys and time.

Any advice would be appreciated.

Topic

[Rob Schepis]

jeff panton wrote:

Philip, what are you referring to by CPL?

I’ve seen CPL referred to as both Critical Parts List or Control Parts List. Think of it as the “ingredients” or “build sheet” of your engine.

[Tony Athens]

Jeff,

You want to solve this issue, RIGHT?

If so, get the props off the boat and take them to a high-end prop shop.. Get them scanned and send the me the scan..

Until you do that, you will accomplish 100% of ZERO..

Let me know when you plan to do this and not screw around with all the rest..

Tony

[Philip]

Engine Model, CPL, serial number. All posted on the metal tag on the engine.

[jeff panton]

Philip, what are you referring to by CPL?

[jeff panton]

No-one is saying its not overpropped, I’m trying to correct the existing problem before removing props and having them adjusted.

[Philip]

You are WAY WAY overpropped if you 2000rpm and 14 gph – end of story.

All the screen shots and videos won’t change that.

What CPL is your engine?

[jeff panton]

Video

Tony,

I ran the boat again today and took some pictures and video that I would like to send you as the videos won’t load here. Where can I send them?

Here are some snapshots though of gauges at different rpm

The first pic is a screenshot of video taken at full throttle. The other three pics are values at 1850rpm.

Top gauge is port

[jeff panton]

Hi Tony,

I’ve owned the boat now for about 6 years.

1. I have never seen 2650-2675 rpm and had no idea it should be getting to that.

2. Never

3. Yes have seen 2500 after new bottom paint, maybe 2 years ago.

4. Yes have seen 2400 recently, early last year.

To be honest I don’t run the boat at WOT often, I usually run the boat at a cruise anywhere between 1800-2000 rpm and on return at WOT for maybe 4 mins or so.

The last time I recorded any GPH, this is what I was obtaining,

11gph @ 19kts (1830rpm)
14gph @ 23kts (2000rpm)
15gph @ 24kts (2090rpm)

[Tony Athens]

Jeff,

I had to go back and re-read all…………………………….It pretty obvious that these engines were totally neglected for close about 15 yrs and you are now playing “catch-up”.. …………………..

Let me ask you these questions & I want accurate answers ..

Also, how long have you owned the boat? Then:

1) Did these engines ever reach 2650-2675 RPM and reach it VERY EASY, in gear loaded as you use the boat………..Notice I said “reach it easy”………….

2) When was the last time you saw 2600 RPM at WOT loaded as you use the boat?

3) When was the last time you saw 2500 RPM at WOT?

4) When one the last time you saw 2400 WPM at WOT?

5) Do you have GPH #’s at various RPM’s ??

Start with these 5 ??’s.

Tony

[jeff panton]

Hi Tony,

Sorry for the late reply.

1. I will take the pictures tomorrow and post them later in the night.

2. Will take off air filter and separator tomorrow as well.

3. The aftercoolers came from a cummins dealer in Miami whom we do business with. We took them apart in our shop as I was sure I read on your technical advice page that they should be prepared and greased as per your advice for easier dismantling in the future. This work was performed by one of my technicians following the instructions from your page.

4. I did another test today and noticed these which I think are worthy of mentioning. The stbd engine with the problem comes up in RPM the same as the port until it reaches about 1350 rpm when it starts to get left behind, it does however climb in rpm from there on quicker than it did before with help from the port engine but at a lower rpm (200-400 less). It will then reach to about 2100 RPM whilst the port is at 2300. At this point the water temperature on the stbd engine climbs to about 15 degrees higher than the port at which time I reduce RPM on both back to 1000 to return to dock. At some points through this range of rpm the boost matches the stbd however at its maximum rpm (2100) it has less boost than port.

As the problem originally occurred after the fuel level was extremely low in the tanks, is it possible that the stbd engine is starving for fuel hence not able to produce the boost. And would this if so cause the egt to be high in turn causing the water temp to rise? Could this have been the original problem and with the high EGT caused the after cooler to crack?

Best,

Jeff

[Tony Athens]

Jeff,

You are now missing something that will turn out to be simple.. Understand you are there a we are here trying to help.

1) Starboard engine has a lot of room around it.. Use that to our advantage and let’s get down in-between the engines with a camera.. Need good pics of all the hose connections, aftercooler install, condensation valve area on the bottom of the new aftercooler, etc,etc etc.. Put my eyes all over that engine as if I was there crawling around..

2) remove the Walker Airsep for now.. I want to see inside the air inlet of the turbo..Leave it off until we test some more.

3) Where did the aftercoolers come from? If new, why did you take them apart? Exactly who did the work?

4) Do you have a good mechanical liquid filled 2.5″ OD 0-30 PSI gauge that you can install on the engine with a 3-10 ft 1/4″ hose? If not get one.. Cheap investment( E-BAY or??) as that will come down to what this will take to sort thru this — some gauges and some sweat equity from you, or a competent mechanic that will listen to input.. .

5) You said nothing has changed–How EXACTLY did you test with the new aftercooler and come up with that conclusion? I want all details..

Tony

[Dave Carlson]

I had a similar problem on a 480 CE and after much searching found this plug missing on the manifold below the air intake. I don’t know if it was a machining hole or had another use. There was a plug for it from Cummins and in stock at the local dealer. I knew the turbo was working, at least I could hear the whine but the boost was going into the engine room.

[jeff panton]

Rob,

Yes all boost hoses and clamps checked, no air leaks found in the system, and yes its behaving EXACTLY as before aftercooler change.

Jeff

[Rob Schepis]

Good turbo pic. Turbo outlet is not your boost issue. Are you 100% sure as to the aftercooler install and no air leaks? Is it acting now EXACTLY as it did before the new aftercoolers?

[jeff panton]

UPDATE

Ok ……….. FINALLY got new after coolers to Jamaica, disassembled and greased as per sbmar after cooler maintenance advice, then installed. STILL no boost from stbd engine 🙁

Removed exhaust riser and took pic of exhaust side of turbo (attached)…….

TOTALLY lost now….

[Rob Schepis]

Be diligent about those 4 exhaust flange bolts at the turbo outlet. Soak them with Kroil or such for some overnights ahead of time. Use a quality 6pt 10mm wrench and tap with a hammer to break them free. Do this BEFORE you start to round off the heads because once they start to get rounded or damaged then things can go down hill fast………

[jeff panton]

Hi Tony,

Yes I will be supervising the work using a mechanic from my Auto Dealership. I am going to remove the exhaust elbows and inspect the turbos and will send pics once I have completed that.

Best,

Jeff

[Rob Schepis]

Propping needs to be on the list..

[Tony Athens]

Jeff,

GOOD PICS–Thanks as now I know what needs to be dealt with.

You have a very clean pair of Cummins 6CTA 480CE’s in a workable engine room.. What that means is you can do what needs to be done and not get bloody knuckles doing it, and when down there doing it, not use many 4-letter words doing it…

Next——————Are you planning to do the work yourself? If so, we will guide you as best possible. If not, do you have a good mechanic that will accept some input?

Give me an idea on how you want to move forward.

As to your exhaust–Yes the factory elbows are far from “lifetime” and will eventually fail, but luckily they are installed, “orientated” as they were designed to be and do not hold water (that’s what the other poster was referring to).. But with that said, once you get thru the current issue, then if you want, we can look at your exhaust system to see if you do have something that will bite your wallet hard should something fail, but only at your request.

I do have more ??’s about your 480CE’s, but that will come as we move forward with a current plan to get you up & running.

Tony

[firehoser75]

Exhaust Elbows

Hi Jeff,
Steep learning curve isn’t it! I know, cause I am on it too. Sorry to be the bearer of more bad news, but your exhaust elbows (stock) are what Tony calls “doomed to fail” and if they are any where near 20 years old probably have at least started the process already. Pull the elbows and have a look at the turbo exhaust side. Take some more photos of the turbo inside and post. I leave it to the experts here to guide you from there.
Good luck,
Tom

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