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View Full Version : LY6 Engine Won't Rev Past 3000 RPMs


Andyg
07-13-2009, 12:56 PM
I was out on the 4th of July with my 2008 PS197 with the LY6. As soon as I took off from the boat launch I new something wasn't right. The engine would not rev over 3000 rpms in gear or in neutral. No engine codes came up that set off the check engine alarm. The engine seemed to run fine except for not going over 3000 RPMs. I checked the fuel pressure and it was over 60PSI. I then disconnected the battery and tried to reset the computer. That didn't work either.

On Monday I took the boat to the dealer closest to where I was on vacation, 2 hour drive one way. When they fired up the boat in the shop it ran fine, saw it with my own eyes in the shop. The technician said there were no engines codes either. The weather didn't permit me to take the boat out the rest of my vacation so I didn't get a chance to see if the problem was gone.

I took the boat out again yesterday and it ran fine for several hours. Then after floating for a while I started the engine back up and the problem was back. Again there were no engine codes that triggered a check engine alarm.

Does anyone have any ideas what could be causing this since no engine codes are present? I am taking it to my local dealer this Friday, but I am concerned that they won't see the problem either. The boat acts like it is in "limp" mode. But my understanding is that for the boat to go into "limp" mode an engine code must be present. The only thing that I can think of is that I got some bad gas and the knock sensor is triggering the boat to cut the RPMs. The frst time it happened was immediately after I filled up with gas. I am now down to a 1/4 tank so if I fill it up with new gas I would think that should eliminate gas as the culprit. Any ideas?

Thanks

Andyg

panamawake
07-13-2009, 04:48 PM
does your boat have perfect pass? the servo might be loose, not an expert but just throwing that out there, did you try accelerating it manually from the motor?

f16driver
07-13-2009, 05:16 PM
Andyg,
What does the motor do when it gets above 3000 rpm....does it pop or backfire or stall or how would you describe it?

F16Driver

Andyg
07-13-2009, 05:22 PM
does your boat have perfect pass? the servo might be loose, not an expert but just throwing that out there, did you try accelerating it manually from the motor?

It is a drive by wire system so the typical servo that controls the thottle cable is not there. Also because it is drive by wire I don't think I can manually accelarate the engine. I will take a look though.

Andyg
07-13-2009, 05:23 PM
Andyg,
What does the motor do when it gets above 3000 rpm....does it pop or backfire or stall or how would you describe it?

F16Driver


If the motor goes above 3000 rpms there are no problems at all, it runs totally normal. In fact when the problem occurs the engine seems to run fine all the way up to 3000 rpms, but just won't go any higher.

panamawake
07-13-2009, 06:37 PM
it could be low oil pressure or high transmission oil temperature if your boat is kicking into power reduction mode which limits your speed intended to allow you to get to shore fix the issue. I would recheck your temperatures and oil pressures.

Andyg
07-13-2009, 06:43 PM
it could be low oil pressure or high transmission oil temperature if your boat is kicking into power reduction mode which limits your speed intended to allow you to get to shore fix the issue. I would recheck your temperatures and oil pressures.

I know for a fact on this setup if there is a high transmission oil temp it will throw a code. On my 2007 with the LY6 I had that exact problem. All fluids checked at the proper level. Oil pressure and engine temp were in normal operating ranges.

f16driver
07-13-2009, 07:00 PM
If the motor goes above 3000 rpms there are no problems at all, it runs totally normal. In fact when the problem occurs the engine seems to run fine all the way up to 3000 rpms, but just won't go any higher.

Are you saying that sometimes the motor just runs fine right up to and above 3000 rpm with no problems and other times it just wont go above 3000rpm? Describe what it does when it wont go above 3000 and you push the throtle further forward?

Andyg
07-13-2009, 09:51 PM
Are you saying that sometimes the motor just runs fine right up to and above 3000 rpm with no problems and other times it just wont go above 3000rpm? Describe what it does when it wont go above 3000 and you push the throtle further forward?

Exactly. If you give it full throttle out of the hole it will actually bounce off 3000 rpms and hop around just below 3000 rpms before settling in. It isn't back firing or making any funny noises up to 3000 rpms. It reminds me of when I miss a shift on my Harley and I am bouncing the engine off the rev limiter. If you give it about half throttle it will climb quickly up to 3000 rpms and just stop. Sometimes if you try and give it more throttle at that point it will also feel like it is hitting a rev limiter and the RPMs will bounce around a little. No matter how much throttle you give it though it won't go over 3000 RPMs.

f16driver
07-14-2009, 07:39 AM
Andyg,
My 2003 Prostar 197 with LQ-9 engine at one time would not go above 3500-4000 rpm. Your description about hitting the rev limiter is similar to my experience. I realize that your engine and mine are different and that your problem could be caused for different reasons. The day my boat started running normally I had done 3 things and I can only guess which item solved the problem. One morning I replaced the fuel pump, the spark plugs and discovered 1 spark plug wire that was faulty. The wire cap was snug and secure on top of the spark plug. But when I was trying to remove the plug wire cap from the spark plug, the wire pulled out leaving the cap sitting on the spark plug. I repaired the wire cutting off the bad end and reinserting the plug wire cap, making it a tad shorter wire. A bad wire may not be noticeable at idle but could present itself at higher rpm. Your boat is basically new and I dont know if your fuel pump suffers from the same fuel pump issues that earlier MC's have, but on mine and alot of others the fuel pump has been a problem. If we ever let the tank get low the pump will suck in debris from the tank bottom and clog the pump. When I removed my pump assembly from fuel tank I found the actual pump inside the casing was not sitting properly secured in the assembly and was able to move around. It wasn't suppose to do that. Sometimes my boat would lose power in a hard turn, maybe it was the pump shifting to one side and fuel flow to the pump was disrupted, maybe...A new pump is really expensive from MC. And last, I replaced all my spark plugs because of a factory recall. I dont know which one item fixed my problem (because I fixed all 3 and then went for a test drive)but your description of your problem sounds similar to my problem. Btw...my boat was was 3 1/2 to 4 years old when this occurred but only had 30 hours on it. I'm betting in my case it was either the plug wire or the fuel pump, but could have been a spark plug. If you havent checked either of these items this might be a place to look. Can you borrow a working pump from a friend. My neighbors and I have a spare pump for swapping and diagnosing pump problems. It takes about 30 minutes to change a pump out on my boat. If you do purchase a new pump assembly from MC dont throw out the old one. Several guys on this forum have rebuilt their pumps using automobile pumps to replace the MC (carter) pump. All of this assumes your handy with tools and are willing to do the work yourself. Obviously working around fuel is not for amature mechanics.
Good luck and don't forget to share with us all what finally fixes your problem.

F16Driver
03 Prostar 197
LQ-9
Fredericksburg VA

JimN
07-14-2009, 07:58 AM
The wire cap was snug and secure on top of the spark plug. But when I was trying to remove the plug wire cap from the spark plug, the wire pulled out leaving the cap sitting on the spark plug. I repaired the wire cutting off the bad end and reinserting the plug wire cap, making it a tad shorter wire. A bad wire may not be noticeable at idle but could present itself at higher rpm.

Did you eventually replace the plug wire or just leave it reinserted? That's not much different from having a bad wire, really. The clip needs to be crimped onto the wire's conductor.

You're correct- at idle, it may idle perfectly but not fire well at high RPM.

f16driver
07-14-2009, 08:26 AM
JimN
I was never able to get MC to send me one wire so I have been using it that way for 2 seasons with no problem. Maybe I'm wrong but IMHO plug wires can be repaired. I've done it on cars before. And you can buy bulk wire and just attach the end caps. There obviously is a correct technique to doing this though.

F16Driver

Andyg
07-14-2009, 10:22 AM
Andyg,
My 2003 Prostar 197 with LQ-9 engine at one time would not go above 3500-4000 rpm. Your description about hitting the rev limiter is similar to my experience. I realize that your engine and mine are different and that your problem could be caused for different reasons. The day my boat started running normally I had done 3 things and I can only guess which item solved the problem. One morning I replaced the fuel pump, the spark plugs and discovered 1 spark plug wire that was faulty. The wire cap was snug and secure on top of the spark plug. But when I was trying to remove the plug wire cap from the spark plug, the wire pulled out leaving the cap sitting on the spark plug. I repaired the wire cutting off the bad end and reinserting the plug wire cap, making it a tad shorter wire. A bad wire may not be noticeable at idle but could present itself at higher rpm. Your boat is basically new and I dont know if your fuel pump suffers from the same fuel pump issues that earlier MC's have, but on mine and alot of others the fuel pump has been a problem. If we ever let the tank get low the pump will suck in debris from the tank bottom and clog the pump. When I removed my pump assembly from fuel tank I found the actual pump inside the casing was not sitting properly secured in the assembly and was able to move around. It wasn't suppose to do that. Sometimes my boat would lose power in a hard turn, maybe it was the pump shifting to one side and fuel flow to the pump was disrupted, maybe...A new pump is really expensive from MC. And last, I replaced all my spark plugs because of a factory recall. I dont know which one item fixed my problem (because I fixed all 3 and then went for a test drive)but your description of your problem sounds similar to my problem. Btw...my boat was was 3 1/2 to 4 years old when this occurred but only had 30 hours on it. I'm betting in my case it was either the plug wire or the fuel pump, but could have been a spark plug. If you havent checked either of these items this might be a place to look. Can you borrow a working pump from a friend. My neighbors and I have a spare pump for swapping and diagnosing pump problems. It takes about 30 minutes to change a pump out on my boat. If you do purchase a new pump assembly from MC dont throw out the old one. Several guys on this forum have rebuilt their pumps using automobile pumps to replace the MC (carter) pump. All of this assumes your handy with tools and are willing to do the work yourself. Obviously working around fuel is not for amature mechanics.
Good luck and don't forget to share with us all what finally fixes your problem.

F16Driver
03 Prostar 197
LQ-9
Fredericksburg VA


F16Driver,
That is pretty much where my thought process went when it first happened. I checked the fuel pressure and it is fine. I actually had the guage connected while out running around the lake.

Yesterday before I posted here I pulled all the spark plugs to inspect them visually. I thought about replacing them, but I didn't have time yesterday. In the process of removing and reinstalling the spark plugs I made note of the plug wire connections to not only the spark plug, but the connection at the coil. I did not feel or see and suspect connections. I still think I might replace the spark plugs regardless in case there is a bad spark plug there, but I don't think it is a bad wire as they all had a positive snap off and back on.

Thanks

Andyg

f16driver
07-14-2009, 10:39 AM
My wires had a positive snap on and off feeling to them also but one wire was making a bad/loose connection above the plug wire cap. If I had only grabbed the cap then I would never have known the wire was loose. It wasnt until I gently pulled the plug wire that the cap came off. If I had never tugged on the wire a little I would not have know the connection was not secure. Obviously with enough force anyone can pull the cap off the wire but I was gently checking and the cap came off in my hand. You can also use and ohmmeter to test for continuity and resistance from one end of the plug wire to the other. I guess I would do that before gently pulling on the ends to see if they're are secure.

Andyg
07-14-2009, 10:55 AM
My wires had a positive snap on and off feeling to them also but one wire was making a bad/loose connection above the plug wire cap. If I had only grabbed the cap then I would never have known the wire was loose. It wasnt until I gently pulled the plug wire that the cap came off. If I had never tugged on the wire a little I would not have know the connection was not secure. Obviously with enough force anyone can pull the cap off the wire but I was gently checking and the cap came off in my hand. You can also use and ohmmeter to test for continuity and resistance from one end of the plug wire to the other. I guess I would do that before gently pulling on the ends to see if they're are secure.

Ya I just pulled on the cap, not the wires. I will get my multimeter out and check continuity on my plug wires. Thanks for the tip.

Andyg

Andyg
07-14-2009, 01:20 PM
F16driver,
I just finished checking the plug wires and they are fine. It was worth a shot.

Thanks

andyg

Andyg
07-18-2009, 12:55 PM
The dealer figured out what was wrong with the boat yesterday. They also could not duplicate the problem as the previous dealer I took it to. They then took the next step and called MasterCraft. MasterCraft was aware of the problem and said that the ECM needs to be updated with a new calibration.

Andyg
07-26-2009, 07:20 PM
Well the problem is back. I had the boat out last weekend and again all day Saturday and after about an hour a half into the day today the boat wouldn't rev past 3000 rpms. I guess it goes back to the dealer for the third time now for this.

f16driver
07-27-2009, 08:31 AM
AndyG,
Sorry to hear about your problem returning. I'm only throwing this out because I've seen it happen twice but never read about it on TMC. What are the chances that your small electric fuel pump, which sits inside the big fuel pump assembly, is loose in the housing assembly and is free to move in the housing? If the electric pump shifts to one side the fuel flow get disrupted and the boat either dies/looses power or wont accelerate.
My neighbor rebuilt his pump this weekend and used the aftermarket auto E2044 from advance auto. There are several threads discusing aftermarket pumps if you havent seen them. It was a little shorter than his previous carter pump and he did not secure it inside the housing like the previous carter. I test drove it for him and had problems keeping the boat running. He removed the pump assembly and secured/stabilized the electric pump in the housing and now it runs great. It also happened on my boat 2 seasons ago.
Just a thought.
Good luck and keep us posted.

F16driver
03 PS 197

Andyg
07-27-2009, 10:24 AM
I don't think it actually is a performance problem with the engine. I believe the computer is just limiting the RPMs. It pretty much runs fine except all of a sudden it won't go past 3000 rpms. My guess is that it has something to do with the TPS sensors between the throttle at the helm and the TPS on the intake. But that is just a wild guess.

I just spoke to my local dealer and they are going to call MC to try and figure out what to do. MC told them that the fix for this was the new engine management program they downloaded into the ECM, however that obviously did not work. So I guess I just have to wait and see what MC thinks now.

Andyg

JimN
07-27-2009, 10:57 AM
I don't think it actually is a performance problem with the engine. I believe the computer is just limiting the RPMs. It pretty much runs fine except all of a sudden it won't go past 3000 rpms. My guess is that it has something to do with the TPS sensors between the throttle at the helm and the TPS on the intake. But that is just a wild guess.

I just spoke to my local dealer and they are going to call MC to try and figure out what to do. MC told them that the fix for this was the new engine management program they downloaded into the ECM, however that obviously did not work. So I guess I just have to wait and see what MC thinks now.

Andyg

When we discussed TBW the last time I went to training, they said the version they were designing had three sets of tracers in the servo and throttle, so that if one or two went bad, it could still go into a default mode to get home. I don't know if they actually use this but I thought I would throw it out there, in case they do. This was before MC actually came out with TBW though, so many things have probably changed.

f16driver
08-07-2009, 09:40 PM
AndyG,
Any luck with your problem?

F16Driver

Andyg
08-08-2009, 01:01 PM
I have not had a chance to get the boat out since they supposedly fixed it again. I will be very surprised if what they did actually solves the problem. The first time I took the boat in they said there was a low oil pressure code. This time there were no codes in the computer. So during the second visit to the shop they focused on the oil pressure sender, but after looking at the sender they said the connectioin was loose. I am sceptical that this is going to fix the problem since there was no code the second time. If the weather ever clears here today I am going to take it out. After the last attempt to fix it I put around 6 hours on the boat before it happened again. I guess we will just have to wait and see.

Andyg

Andyg
08-16-2009, 11:30 AM
Well I have had the boat out twice since the dealer fixed the oil pressure sender connection and I have not had a problem since. I still have my fingers crossed that the problem is fixed.

MCVOLS
08-30-2009, 10:30 PM
Have you had any more issues since your most recent dealer visit? I found this thread because my MCX is doing this on my boat. I am calling the dealer Monday, but thought I would ask.

Andyg
08-30-2009, 11:36 PM
Have you had any more issues since your most recent dealer visit? I found this thread because my MCX is doing this on my boat. I am calling the dealer Monday, but thought I would ask.

I have only had the boat out twice since that last time it was at the dealer. The weather around here has not been cooperating with my skiing schedule. It appears that the problem has been fixed, in this case a loose connection on the oil pressure sender.

Andyg

rem_pss308
09-06-2009, 07:32 AM
AndyG: Have you had the boat out again ?
How is it doing. Im having the same problem with my LTR

JimN
09-06-2009, 08:26 AM
AndyG: Have you had the boat out again ?
How is it doing. Im having the same problem with my LTR

Check the fuel pressure. The oil pressure sender won't cause your motor to have limited RPM.

f16driver
09-06-2009, 08:56 AM
AndyG,
Did the dealer ever offer up an explanation as to why the oil pressure sender connection was causing your boat rpm to not go past 3000 rpm? Was the sensor connection causing a faulty check engine light or telling the ECM to reduce power and putting the motor into limp home mode? How did the repair guys explain your problem? I'm curious because of JimN's previous post.


F16Driver
03 PS 197 w/LQ-9

JimN
09-06-2009, 09:24 AM
My post was in response to the LTR, not LQ-9.

Andyg
10-12-2009, 08:16 PM
Well it looks like the problem is back. I had not used the boat since the end of August until today when I winterized it. I had an overheating problem that took me an hour to solve. It happens when there is an air pocket somewhere in the system and I can't get it out. After an hour of disconnecting hoses and checking to make sure all the hose clamps were tight I finally fixed it. Well during that process the engine went into limp mode and wouldn't come out again. I can't imagine that it is due to the high temp issue I was running into since the alarm never sounded, temp never got over 170. Unfortunately I am taking it up to where I store it for the winter tomorrow so the delaer won't get a chance to look at it again until spring.