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502 mpi problem!!! HELP!!!!!

Old 05-23-2010, 07:02 PM
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Default 502 mpi problem!!! HELP!!!!!

So I just installed a rebuild gen 5 502 mpi mag in my baja, and I am having some issues with it not reving over 3000 rpm.. When you take off its fine, it will run just fine till it hits 3000 and its like it cuts the ignition off, like its not advancing the timing. I have removed the vst tank, and am running just a electic fuel pump. The boat runs awsome in the idle too 2900 rpm, but as soon as it hits 3000 it cuts it off, and just like bogs till it hits about 1700 rpm then it come right back to life..and runs fine...PLEASE ANYONE HELP!!!!
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Old 05-23-2010, 07:14 PM
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Originally Posted by stlliberator
So I just installed a rebuild gen 5 502 mpi mag in my baja, and I am having some issues with it not reving over 3000 rpm.. When you take off its fine, it will run just fine till it hits 3000 and its like it cuts the ignition off, like its not advancing the timing. I have removed the vst tank, and am running just a electic fuel pump. The boat runs awsome in the idle too 2900 rpm, but as soon as it hits 3000 it cuts it off, and just like bogs till it hits about 1700 rpm then it come right back to life..and runs fine...PLEASE ANYONE HELP!!!!
did you check fuel pressure? sounds like not enough pump to keep up,also where is the fuel pump?
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Old 05-23-2010, 08:06 PM
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I have a factory merc pump for a 280 outboard, its mounted on the transom right back by the fuel rail..I used the factory fuel rails...why would it have enough presure when its has a lot of load on the motor when coming on plain but when im on plane and try to go past 3 grand it cuts out?? What kinda pressure do I need???
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Old 05-23-2010, 08:27 PM
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If your drive lube is low the engine will not run over 3000 rpms, check it.
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Old 05-23-2010, 09:21 PM
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how will the engine know if the drive lube is low or not?? Will it cut out at 3000???
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Old 05-23-2010, 09:26 PM
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If you have a drive lube reservoir there is a sensor in it. It will cut out at almost exactly 3000 rpm.
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Old 05-23-2010, 09:28 PM
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I dont have a drive lube rez tank, the boat is a 88 and the motor is a 96, so I would asume that in 96 the bravo had a rez tank for the outdrive, but mine doesnt..how can I fit it, and what wire on the wiring harness should go to the tank...
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Old 05-23-2010, 09:36 PM
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If it doesn't see the sensor I don't think it should kill the engine at 3000. I'll see if I can look it up in the manual and let you know.
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Old 05-23-2010, 09:42 PM
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ya I wonder if since its not conected it thinks its low, or bad..so its cutting the ignition out...cause when the motor is in nutral, you can rev it way past 3000 with no problem..


another thing, does anyone think that I might have the pump mounted to high? Its mounted right behind where the vst tank was mounted on the motor, just screwed to the transom, and Im useing the factory leads that were on the vst tank, to power the new pump...think maybe that has something to do with it??
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Old 05-24-2010, 01:15 AM
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Originally Posted by stlliberator
I have a factory merc pump for a 280 outboard, its mounted on the transom right back by the fuel rail..I used the factory fuel rails...why would it have enough presure when its has a lot of load on the motor when coming on plain but when im on plane and try to go past 3 grand it cuts out?? What kinda pressure do I need???
You have a pump made to supply fuel for a 280hp outboard and you have a 415hp I/O. Probably can't push enough volume of fuel.
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