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View Full Version : Problems with my MCX enigine - need help


Reto
10-01-2007, 07:36 AM
Hallo, i have a MC X-2 2006 with 300 hrs.

Since weekend i have a problem with my mcx engine. The engine does not go over 4000 rpm. If it reachs 4000 rpm it goes down to ~3700 rpm and starts to go up and down between 3700 rpm and 4000 rpm. The engine sounds not good if i reach the 4000 rpm. Can that be a limiter, if the engine has same problems?

My dealer is 4 hours away - so maybe you can help me with some advices. Anyone had the same problem??

Sorry for my bad english, i hope you can understand, what my problem is.:(

Reto
10-01-2007, 07:39 AM
"Ceck engine" displays if i reach 4000 rpm.

bigmac
10-01-2007, 08:13 AM
In addition to a max RPM limiter, they do have a rev limiter that is variable according to engine temp - it won't allow full throttle until the engine reaches it's appropriate operating temp, and the RPMs are phased according to the actual temp sensed by the engine:

103F (40C) or less: 3,000 RPMs
104 to 139F (41 to 59C): 4,200 RPM
140 (60C) and higher,: Full RPM

So, what engine water temps are you indicating? Could you have a bad thermostat that's sticking open and keeping it from reaching 140 degrees?

Reto
10-01-2007, 10:11 AM
Just tried it out. After 1/2 hour the engine just reaches ~110F.
Cold water, but it seems to be the problem.

THX bigmac!

BuoyChaser
10-01-2007, 10:21 AM
Just tried it out. After 1/2 hour the engine just reaches ~110F.
Cold water, but it seems to be the problem.

THX bigmac!
temp should be at 160F once it is warm...sounds like a stuck thermostat maybe, but usually that means it runs hotter?!?have you checked the bottom intake, or followed the intake hose line???maybe some weeds plugged in the transmission cooler...

how many hours do you have on it???

have you tried disconnecting the battery cables to reset the computer system???

Sodar
10-01-2007, 10:34 AM
temp should be at 160F once it is warm...sounds like a stuck thermostat maybe, but usually that means it runs hotter?!?have you checked the bottom intake, or followed the intake hose line???maybe some weeds plugged in the transmission cooler...

how many hours do you have on it???

have you tried disconnecting the battery cables to reset the computer system???

You are right on the engine running warmer at times running with a stuck thermostat, or no thermostat at all, but from what I have heard and experienced, your will not see you water temp climb, your engine will just be running warmer. Basically, the cooling water is not staying in the motor long enough to pull heat from the motor, it is just rushing by... staying at a low temp.

JimN
10-01-2007, 11:13 AM
Check your impeller and oil cooler. If there's no raw water coming in, the temperature won't be normal and the motor will cook. The RPM reduction will make it sound bad and you need to stop running it in hopes that it'll get better. Once the impeller has been changed, change your oil and filter, too.

Buy a impeller with a gasket- always use a new gasket. A stuck thermostat will only run hot if it never opens and no thermostat will just pass raw water right through the motor, so it'll never get hot unless the path to the motor is blocked.

beatle78
10-01-2007, 11:26 AM
If water is getting through the system, couldn't the thermostat be stuck open and that is why the temp is never reaching 160F?

rektek
10-01-2007, 11:27 AM
thermostats can stick in the open position, in fact I see this more often than sticking closed.;)

Diesel
10-01-2007, 11:35 AM
Basically, the cooling water is not staying in the motor long enough to pull heat from the motor, it is just rushing by... staying at a low temp.

I might not be understanding you point but this is incorrect. A open tstat will easily over cool the engine.

Reto
10-01-2007, 11:36 AM
have you tried disconnecting the battery cables to reset the computer system???

Yes. But no difference.

JimN
10-01-2007, 11:54 AM
Reto- if there is a lot of plant material in the water where you use the boat, it can get lodged in the motor and cause these problems. Removing the impeller and checking the oil cooler will remove any doubt about those. Also, plastic bags in the water may be hard to see but they can be sucked into the raw water grate on the hull. This will cause the same problems. Running the motor with no cooling water will damage the exhaust system, as well as the impeller, gaskets, motor and oil.

bigmac
10-01-2007, 12:15 PM
So, you're saying that the engine is maybe actually overheating despite3 the temp gauge reading 110. And that overheating is due to plugging of water circulation from intake occlusion or thermostat stuck closed, so that there's no water circulating, so the temp gauge is reading artificially low?

Hmmm....

Sodar
10-01-2007, 12:20 PM
I might not be understanding you point but this is incorrect. A open tstat will easily over cool the engine.

Not exactly true. We run no thermostat in my dad's Twin Turbo motor. His water temp usually runs about 60 degrees over the lake temp. However, his oil temp and header temp run the same as if he had a 180 degree thermostat in place. In his motor, all though the water temp is staying cool, the engine temp is running in its normal range.

JimN
10-01-2007, 12:35 PM
bigmac- the sensor is made to be immersed in liquid, not surrounded by air. Much better heat transfer in a liquid, so yes, it can read way low and be overheating.

Sodar- One think I don't like about running without a thermostat is that the cooling water temperature is a lot lower than what would normally be in the motor and the rapid, large temperature swing can cause problems after a really hard run.

MYMC
10-01-2007, 12:36 PM
So, you're saying that the engine is maybe actually overheating despite3 the temp gauge reading 110. And that overheating is due to plugging of water circulation from intake occlusion or thermostat stuck closed, so that there's no water circulating, so the temp gauge is reading artificially low?

Hmmm....
The sensor is designed to read "water temp" not "air temp"...if there is no water then you'll get an artificially low reading...happens with race cars all the time, radiator gets a hole put in it and the temp gauge will never move.

rektek
10-01-2007, 12:57 PM
The sensor is designed to read "water temp" not "air temp"...if there is no water then you'll get an artificially low reading...happens with race cars all the time, radiator gets a hole put in it and the temp gauge will never move.

this is true, however there are other obvious signs when a engine is overheating. engine knocking, manifold paint peeling, blazing hot engine compartment etc.

I agree with Jim N, running without t-stats is never a good idea in any water cooled engine. lots of expansion and contraction going on inside a combustion engine, running without a t-stat is asking for premature engine wear.

J:o

beatle78
10-01-2007, 12:57 PM
bigmac- the sensor is made to be immersed in liquid, not surrounded by air. Much better heat transfer in a liquid, so yes, it can read way low and be overheating.

Sodar- One think I don't like about running without a thermostat is that the cooling water temperature is a lot lower than what would normally be in the motor and the rapid, large temperature swing can cause problems after a really hard run.


ohhhhh... now I get it.

For your sake I hope you haven't been running around with no water going through the block :o

bigmac
10-01-2007, 01:19 PM
I realize that temp sensors read water not air. I don't think it's the most likely scenario for his RPM limiting in this case, but acknowledge that it's possible. Clearly his troubleshooting should include clearing the transmission cooler and replacing the RW impeller, in addition to a new marine thermostat.

MYMC
10-01-2007, 01:29 PM
this is true, however there are other obvious signs when a engine is overheating. engine knocking, manifold paint peeling, blazing hot engine compartment etc.J:o
I wasn't diagnosing the problem...I was addressing the question about the possibility that the system could be over heating while the gauge says everything is fine.

Reto
10-01-2007, 04:09 PM
Thanks for your advices and tipps!!

The engine shows no signs of overheating so first step in troubleshooting will be a new thermostat. Hope that will help...:)

JimN
10-01-2007, 04:22 PM
Actually, overheating causes the ECM to keep the RPM below a certain point by alternately switching one bank of injectors off and on. This causes it to run rough and sluggish above mid-RPM.

First step should be to inspect the impeller and oil cooler. If they're OK, then look into the thermostat.

Also, check your battery connections and the ground (earth) connections on the back of the motor.

If it stumbles when you try to move, make sure the battery terminals are still solidly fixed in the battery case. Rare, but it happens. Saturday night, I tried to start my truck and when I turned the key, all of the lights went out and when I turned the key back, they came on again. I checked the cables for tightness and the positive insert came right out of the battery case. The only indication of a problem, in hindsight, was a slight stumble from a standstill and occasionally, the sound from my stereo would drop out and come back to normal. No cranking issues, no dead battery, no lights flickering, nothing else.

MYMC
10-01-2007, 04:35 PM
Actually, overheating causes the ECM to keep the RPM below a certain point by alternately switching one bank of injectors off and on. This causes it to run rough and sluggish above mid-RPM.

First step should be to inspect the impeller and oil cooler. If they're OK, then look into the thermostat.

Also, check your battery connections and the ground (earth) connections on the back of the motor.

If it stumbles when you try to move, make sure the battery terminals are still solidly fixed in the battery case. Rare, but it happens. Saturday night, I tried to start my truck and when I turned the key, all of the lights went out and when I turned the key back, they came on again. I checked the cables for tightness and the positive insert came right out of the battery case. The only indication of a problem, in hindsight, was a slight stumble from a standstill and occasionally, the sound from my stereo would drop out and come back to normal. No cranking issues, no dead battery, no lights flickering, nothing else.
Jim,
Ever seen how one of these runs with an exhaust leak?

JimN
10-01-2007, 04:44 PM
No, is it the same as what he described?

MYMC
10-02-2007, 09:41 AM
No, is it the same as what he described?
Pretty much, it'll run fine when first fired and then slowly lose RPM until it just stays around 3500 and runs rough. You shut it down open the hatch and find nothing...restart and the cycle begins again. It may not be the problem here but until you've seen it, it is fun to diagnose.

NeilM
10-02-2007, 10:02 AM
Assuming enough tests have now been done to determine it's not rev limiting from overheating,

I'd look to restricted fuel flow next. Perhaps an almost - plugged screen?

Reto
10-14-2007, 03:24 AM
Yesterday i chanced the thermostat and now the engine is working at the right temperature. the temp is exactly 160 F. :) The old thermostat was broken.

BUT: the problem is not gone. the engine does not go over 4000 rpm. same failure as i described in my first post.. :mad:

Do you know if i have to delete the error in the computer?? (my dealer is far away - so that could be a problem for me)