480CE RPM jumps 100-200 every now and then ?

[Greg Weaver]

Hello all, 2003 Carolina Classic 480CE

I have searched the forum here and google and have found similar issues of rpm dropping but my hiccup is it jumps up some.

I have had this problem on and off for a year now, it comes and goes.
It will not do it at idle in the slip.
It happens when i’m trolling at low rpms
I turned my engine sync off and have isolated it to the starboard engine 100%.
Racors are checked daily as I charter the boat and it is part of my routine check EVERYDAY
Racors are crystal clean
Last chance filter is brand new and last year i had the problem prior to changing it and directly after changing it

I watch my rpm jump and the recover moments later and I also feel it in the seat of my pants.

Port engine is a fresh rebuild with 600 hours on it, no black smoke at throttle up

Starboard engine has 2996 hours on it and runs like a sewing machine other than this hiccup
Starboard engine has some black smoke on throttle up, unless I bring it up really slow and it will have none

Props are perfect as per Tony’s fuel burn specs and both engines reach 2690-2700

It’s not a huge issue but when theres something not perfect, it bugs me and I would like to figure it out

My thoughts on possibilities are as followed

Also I might add, that all similar problems that i have read, are all starboard engine related.

Possible ground or loose wire?
Maybe a bad injector
Do these engines have a throttle position sensor ?
Throttle linkage looks fine

If anyone can chime in on things for me to consider I would sure appreciate it.

Thanks all

Greg

Topic

[Greg Weaver]

Well I’m happy to say, 2 full days with ZERO hiccups in the RPM’s jumping around

I am confident the issue was a bad connection at the engine harness

Thanks all for chiming in

And another big Thank you to Tony pointing me in the correct direction
Greg

[Greg Weaver]

I got it all cleaned up real nice like and zero issues today, I will get some dielectric on it tomorrow,

I’ really hope I got the problem solved, tomorrow will be a good test but nevertheless I’d like to thank you for you putting in your time with me

Greg

[Tony Athens]

Hard work on your side and a never give up attitude = found “green stuff” on some wires / connections = clean it all up and use a petroleum based dielectric = no more issues = long term solution

I’ll bet you got it! We are talking Millivolts and Milliamps–All connections must be 100%, and a dielectric close to insures it with stay that way for years.

[Greg Weaver]

Tony,

So a bit of a follow up, in the beginning of this thread I forgot to mention that while i’m at cruise, 2380 every now and then it will jump up to like 2440 then recover and repeat.

After you mentioned the potentiometer, I bought 2 of them and replaced the one I thought was faulty and then the next day it acted right back up again.

I sat there staring at my engine as to what the heck could be going on, so I pulled out a mirror and traced the potentiometer wire back to where it ties into the engine harness. I unplugged it and and put a magnifying glass on it with flashlight and i did have significant corrosion on it,, a whitish / greenish film on it. I cleaned it up very good and plugged it back in last night.

Today I had a wreck fishing trip out 30 miles, it never acted up once at cruise and I did troll a mile from one wreck to another and again never acted up. Today was the first day in many many days I have not had this act up, tomorrow will be the test again as I have a few inshore trips with lots of trolling.

I will keep you all posted as to the progress as I hate when someone post a problem they have with no follow up on the fix

P.S. Brent, I can still pronounce potentiometer, man this is a tongue twister for me LOL

Thanks all

[Jason t]

Well dang….my starboard 450 (2001 Carolina classic) is doing the same thing at cruise right now. Not going to hi-jack your thread but mine did a 100-200 rpm drop and pick up at 2200 cruise the other day. Happened right after I transferred fuel From the saddle tanks while under power and It continues on and off for the next 2 hours of run time. Fueled up…issue resolved itself for my last 45 minutes of cruise.

Crossing my fingers it doesn’t come back but this coming weekend will be running it for about a 120 miles of cruise time so we shall see if it acts up again.

Responding…so I can subscribe.

[Greg Weaver]

Welp, I installed the new potentiometer and I still have the problem.

My first 10 minutes of trolling were great and i was happy till it happened again, acted up a small amount for 15 minutes and then disappeared for 8 or so hours, then at the end of the trip I got up on plane for about a 1/2 mile and when I brought the throttles back it appeared again LOL

Possible bad injector ??

Thanks all

[Tony Athens]

Throttle Pots

The throttle “sensors” are mechanical parts and subject to internal wear.. I’ve had 3-4 go out over the last 15 yrs or so, but were usually related to moisture issues. Let’s both hope that solves the glitch..

[Greg Weaver]

Thank you,

at idle im smooth as silk steady at 600 rpm or 580 in slow idle

I’m really hoping it the sensor that i just purchased

[JJM]

Scanner

Do you have diagnostic ports at the help? Round ports with I believe 7-9 pins? If you do then the scanner will work . If you do not then it would be a waste of money. Let me know.

[JJM]

Sounds like you are on to the right path…

Greg Weaver wrote:

I have no check engine light for this hiccup in rpm jump

I am certain about my fuel delivery and all filters be correct

Something was telling me this was electronically related based on how it comes and goes and after learning about the potentiometer, It makes great possible sense i’m onto something thanks to Tony.

I bought 2 of them in hopes that this is the gremlin and if not, i’m only out $80.00 bucks + shipping

This rack adjustment you speak of is interesting, do you have the 480CE’s ? I googled it and boat diesel came up and I can’t view the thread so i’m baffled about this adjustment, might you kindly describe this in more detail please ?

Greg

Sounds like maybe you will get it. Let us know.

The rack adjustment is quite easy but very small changes can cause big results so go very slow. If the boat is not hunting at idle then I would say its likely not the rack.

The way you adjust it is remove the cap, use a 90 degree flat screw driver and make every so slight turns clockwise or counter clockwise.

See attached

[Greg Weaver]

JJM,

please tell me more about this scanner you speak of and where to get one, i’m sure it will come in handy at some point

Greg

[Greg Weaver]

I have no check engine light for this hiccup in rpm jump

I am certain about my fuel delivery and all filters be correct

Something was telling me this was electronically related based on how it comes and goes and after learning about the potentiometer, It makes great possible sense i’m onto something thanks to Tony.

I bought 2 of them in hopes that this is the gremlin and if not, i’m only out $80.00 bucks + shipping

This rack adjustment you speak of is interesting, do you have the 480CE’s ? I googled it and boat diesel came up and I can’t view the thread so i’m baffled about this adjustment, might you kindly describe this in more detail please ?

Greg

[Greg Weaver]

Tony,

I just bought 2 of those as per your advice if it’s not the problem, im only out a few bucks

Greg

[JJM]

Awesome

Well looks like you are on to something maybe….. Do you have a check engine light on? A scan would probably show a faulty TPS if it was.

Ya after studying your photos a bit closer looks like the shifting at least is controlled by a cable. My boat came with digitial shifters from factory.

One other thought…………”hunting ” at low rpms can often be an issue with a rack adjustment. I played around with this a week ago when trying to narrow a issue with a sensor and adjusted the rack. Once the rack got “looser” engine would ocassionally hunt. There was a fine line between hunting and running smooth but still allowing rack to move freely. Search 480 CE Rack adjustment and you will find it. 17 mm box wrench to take cap off and a 90 degree flat bit screw driver to adjust it. Super sensitive so go slow and mark your starting point.

[Tony Athens]

Good find———–Buy 2, maybe 3 at that price.. Super cheap compared to upgrading.

1 user thanked author for this post.

Greg Weaver

[Greg Weaver]

Thank you

So I got the numbers off the back of the potentiometer ” CTS PBT-G30 ”

I googled it and came up with CTS PBT-G30 Throttle Position Sensor TPS

$ 39.00 Old new stock so I think I will buy it for the heck of it and give it a go

I would love to get my throttle and gear to operate via electronically like yours, sounds like an expensive venture though.

[JJM]

electronic throttles and shifters.

On my boat with the 480 CEs my shifters and throttles are electronically controlled. Being that the 480 CE is mostly electronic controlled yours like are as well. There are 2 solenoids on each transmission that control the gear shift. The throttles from what I can see and understand are electronically controlled also through the computer and controls the governor. I remember seeing the transmission solenoids the other day. I also found a scanner that will read almost all parameters of the 480 both codes and live data if you need to do that. I am sure there is throttle percent on there as well. It helped me track down a faulty rack sensor on my pump. Pretty amazing technology for 2004. Hope this helps you.

[Greg Weaver]

Tony,

I follow what your saying, same as swapping a coil to a different cylinder to see if the code follows

This is a small glitch that I think I can live with unless overtime I’m creating a bigger issue, some days it doesn’t even do it, I’m quite in tune with my boat and I do notice when it happens

In your opinion, is this something I should immediately address ?

Thanks for you time Tony I really do appreciate you input more than you know

Greg

[Tony Athens]

All is good and I do understand that it takes time to learn you boat.. This has nothing to do with being a diesel mechanic, it’s just about learning all the system on the boat–You are are doing just fine……………..So me bad that way–sorry.

Your current picture says it all..

These are the ” potentiometers” that control the RPM of your engines..Its a mechanical variable resistor..

1st thing I’d do is swap them to see that the unit follow the symptom.. But of course, you have to decide if what is happening bugs you enough to go thru where this may be going..

Tony

[Greg Weaver]

Tony,

I am learning the boat the best I can Tony and I assure you I do my best, but I am no Diesel mechanic by any means. the picture i’m posting is a bit dark because they were tucked away quite well against the firewall, so please excuse my thick headed ignorance if you could

Yes the previous owner let the Ethylene Glycol level get a bit low and the aluminum canister was not pressurized, I did fill it accordingly and re-pressurized it to spec post on canister. and have never had any issues other than this hiccup

I pray this is what your wanting to see in order of avoiding more public embarrassment.

I can certainly go back down and take a better picture if need be with the flash on, i didn’t realize it was so dark until I got home to send it to you

Greg

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