Mercruiser 7.4L MPI slowing down
#41
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I'd find a new marine tech. The part # they gave you is for the entire throttle body.
The TPS is clearly listed as a separate part https://www.mercruiserparts.com/bam/...31918/2705/100
The TPS is clearly listed as a separate part https://www.mercruiserparts.com/bam/...31918/2705/100
#42
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hey that’s great to know. During troubleshooting did the bad ECM throw any error codes? I guess if that’s not working correctly anything is suspect.
#43
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I have not tried that. Someone also suggested taking the engine cover off too if it’s a thermal issue. It’s worth a shot. Thanks
#44
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I don't remember. All I know is a buddy of mine was a Merc tech at a local boat dealer and I told him what it was doing. He called Merc and they said it was a known problem with some of the ECM's on the 7.4L MPI's and they wanted the old ECM shipped to them and they shipped a new one at no charge.
#45
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you cant just replace the TPSensor it has pivot points that allow for adjustment, it needs to be calibrated with a scanner or laptop....and as stated find another marine Tech
Last edited by F-2 Speedy; 07-31-2019 at 08:04 AM.
#46
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If there is a possibility that the ECM is acting up when it gets hot I would get a can of Freeze it Spray and when it acts up try cooling off the ECM and see what happens. That is almost what it sounds like is happening even though you are not getting any codes.
Not sure where you can find it local, maybe a 2-way radio shop.
https://www.crcindustries.com/produc...-oz-14086.html
Not sure where you can find it local, maybe a 2-way radio shop.
https://www.crcindustries.com/produc...-oz-14086.html
#47
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I don't remember. All I know is a buddy of mine was a Merc tech at a local boat dealer and I told him what it was doing. He called Merc and they said it was a known problem with some of the ECM's on the 7.4L MPI's and they wanted the old ECM shipped to them and they shipped a new one at no charge.
I did call Mercury unfortunately they don’t have the part (they stopped making MEFI around same time you had issue) but they did point me to a third party that rebuilds ecms.
I think we might be on to something here I appreciate your info.
#48
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I had exactly the same problem on a 1999 7.4 in a baja. After searching fuel pressure, tps, etc... it turned out that my exhaust manifolds and risers were clogged with rust. My fault for not changing them every couple years. Installed new manifolds and risers and it ran perfect. Next time it looses power,shoot a heat gun on the risers and if it’s anything like mine they will be extremely hot. Also when it looses power, let it idle for a while to allow the manifolds to cool then then throttle up and see how it runs. Again, if it’s like mine it will run fine until the manifolds heat up. Good luck
#49
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Interesting....good thread !
#50
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I had exactly the same problem on a 1999 7.4 in a baja. After searching fuel pressure, tps, etc... it turned out that my exhaust manifolds and risers were clogged with rust. My fault for not changing them every couple years. Installed new manifolds and risers and it ran perfect. Next time it looses power,shoot a heat gun on the risers and if it’s anything like mine they will be extremely hot. Also when it looses power, let it idle for a while to allow the manifolds to cool then then throttle up and see how it runs. Again, if it’s like mine it will run fine until the manifolds heat up. Good luck
Frustrating that you both had same issue but different causes. I think I’m going to have them check those other things before replacing ECU though.