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454 MPI rpm issue

Old 08-10-2020, 11:55 AM
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Default 454 MPI rpm issue

I got a new to me 99 baja outlaw 25 and it came with a 454 mpi and a 21p prop. At WOT I only hit about 41mph and 4000 rpm, which seems low for this set up. I have friends with the same boat running a 23p prop running 4800 rpm in the 50's. I have changed the fuel filter as well as the ignition module (thinking it wasn't getting advanced timing) and not much change. I have the base timing set at 8 deg and thats about all you can adjust on it. I hooked up a fuel pressure gauge on the schrader valve on the top of the engine and it was about 48 at WOT. From what I'm reading, I should be closer to 4800-5000 rpm at wot. After planning, I trim up and see some gain in rpm but it maxes out around 4000. It seems like I'm getting fuel and timing, but not sure where else to check. Any help would be appreciated, thanks!

The previous owner said he had just gotten a tune up beginning of the season. New plugs, distributor cap, fluids, etc...
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Old 08-10-2020, 12:44 PM
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Yes, your WOT rpm should be 4800-5000, and it should turn the 21 easy up there unless the drive ratio has been changed from 1:50

What do the plugs look like?

Do a compression test
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Old 08-10-2020, 12:47 PM
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Is it a 7.4 mpi or a 454 mag mpi??
Did you put it into base timing mode when you set the timing??
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Old 08-10-2020, 01:23 PM
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I set the base timing at 8 deg with it in service mode
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Old 08-10-2020, 01:23 PM
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it's a 7.4 MPI
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Old 08-10-2020, 01:25 PM
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sorry Im a new member so I gotta have the 10 posts before a pic lol
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Old 08-10-2020, 01:26 PM
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Old 08-10-2020, 02:46 PM
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Old 08-10-2020, 02:47 PM
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Old 08-10-2020, 02:56 PM
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pic of plug #1

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