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-   -   RPM's suddenly limited at 2000 RPMs (http://www.mastercraft.com/teamtalk/showthread.php?t=57559)

MrTsuth 09-23-2013 09:49 PM

RPM's suddenly limited at 2000 RPMs
 
I have a 1996 Maristar 225v... It ha run flawlessly all summer long. It missed about 2 weeks between use due to weather... Suddenly, the engine will not throttle higher than 2000 RPMs... I can't tell if it is flooding or starving... Or if there is some sort of safety that is limiting it.... Any suggestions on what it may be and where to begin my troubleshoot?

Ski-me 09-24-2013 09:48 AM

The LT1 probably went into Limp mode (I've experience it too). Check your T-stats for the correct ones (and no blockages), check your intake impeller and be sure there is not any debris in there. It's very sensitive to engine temps and this can happen. Also might want to replace your temp sensor for good measure too.

These are just generic, basic answers to this problem but a place to start. T-stats should be 142 and 160 with a hole drilled in the top.

skitilldark 10-02-2013 12:05 PM

Quote:

Originally Posted by MrTsuth (Post 980573)
I have a 1996 Maristar 225v... It ha run flawlessly all summer long. It missed about 2 weeks between use due to weather... Suddenly, the engine will not throttle higher than 2000 RPMs... I can't tell if it is flooding or starving... Or if there is some sort of safety that is limiting it.... Any suggestions on what it may be and where to begin my troubleshoot?

You have a perfect pass?

neil.anderson63 10-02-2013 12:53 PM

Are you saying it is going into limp mode? Mine behaved similar to this and it was a bad battery in my 2 battery system. Replaced the bad battery, no trouble since.

MrTsuth 10-06-2013 07:52 PM

I don't have a perfect pass.... I disconnected the battery and reset the limp mode.... Took it out and it ran perfect for about 15 minutes... Then suddenly got hot and went in to limp mode again.... I noticed that at the same time, the oil pressure dropped significantly at the same time.... I'm thinking that I have some blockage in my raw water intake line has some blockage at the oil cooler.... Could this be the cause??? The blockage at the oil cooler does not allow the oil to cool enough... Letting the oil get too hot, and thin, causing it to go in to limp mode????

JimN 10-06-2013 08:25 PM

Quote:

Originally Posted by MrTsuth (Post 980573)
I have a 1996 Maristar 225v... It ha run flawlessly all summer long. It missed about 2 weeks between use due to weather... Suddenly, the engine will not throttle higher than 2000 RPMs... I can't tell if it is flooding or starving... Or if there is some sort of safety that is limiting it.... Any suggestions on what it may be and where to begin my troubleshoot?

2000 RPM is the magic number for overheat-induced RPM reduction, especially if it runs lumpy when this happens. Make sure the impeller is good, the raw water pump cover is tight and well-sealed and no rubber parts from an old impeller are clogging the thermostat(s) or passages. If that is good, look at the wires going to the ECT (Engine Coolant Temperature) sensor. If the wires going to it have melted due to a bad engine overheat, it will tell the ECM that it's overheating, even if it's not. If the wires are good and the plug is fully engaged, measure the sensor's resistance- I have posted a chart here so many times without a mod making it a sticky that there's no reason I should have to do it again.

JimN 10-06-2013 08:26 PM

Quote:

Originally Posted by MrTsuth (Post 983327)
I don't have a perfect pass.... I disconnected the battery and reset the limp mode.... Took it out and it ran perfect for about 15 minutes... Then suddenly got hot and went in to limp mode again.... I noticed that at the same time, the oil pressure dropped significantly at the same time.... I'm thinking that I have some blockage in my raw water intake line has some blockage at the oil cooler.... Could this be the cause??? The blockage at the oil cooler does not allow the oil to cool enough... Letting the oil get too hot, and thin, causing it to go in to limp mode????

The oil cooler isn't for the engine, it's for the transmission.

MrTsuth 04-13-2014 03:27 PM

Quote:

Originally Posted by JimN (Post 983332)
2000 RPM is the magic number for overheat-induced RPM reduction, especially if it runs lumpy when this happens. Make sure the impeller is good, the raw water pump cover is tight and well-sealed and no rubber parts from an old impeller are clogging the thermostat(s) or passages. If that is good, look at the wires going to the ECT (Engine Coolant Temperature) sensor. If the wires going to it have melted due to a bad engine overheat, it will tell the ECM that it's overheating, even if it's not. If the wires are good and the plug is fully engaged, measure the sensor's resistance- I have posted a chart here so many times without a mod making it a sticky that there's no reason I should have to do it again.

Put the boat away for the winter... Just got it back out and am now working on it again.... Before I took the boat out, I changed the coolant temp sensor and the pigtail. For good measure, I changed the thermostat located just under the air filter... (Not sure where the other one is located)... I have also installed a new impeller...

Still overheating... Any more suggestions before I have to break down and take it in to the dealer??

mgs96ps 04-13-2014 03:44 PM

The 143 is in the mixer right in front of engine water pump and directly above impeller pump.

JimN 04-13-2014 04:08 PM

Quote:

Originally Posted by MrTsuth (Post 1033093)
Put the boat away for the winter... Just got it back out and am now working on it again.... Before I took the boat out, I changed the coolant temp sensor and the pigtail. For good measure, I changed the thermostat located just under the air filter... (Not sure where the other one is located)... I have also installed a new impeller...

Still overheating... Any more suggestions before I have to break down and take it in to the dealer??

Overheating, after how long? Is this in the water, or on a trailer? That sender you replaced- one wire? That one doesn't matter for what the ECM reacts to. You need to be concerned with the one that has two wires- one wire is yellow and the other is black.

Do you have a multi-meter? When it's cold, connect it to a water source (NOT A FAKE-A-LAKE!!!!!!!!!), let it idle and immediately remove the harness from the two-wire temp sender so you can measure the resistance of the sender. Post the resistance.

Have you replaced the water circulating pump? If so, did you use an LT-1 pump? You absolutely have to.


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