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454 MAG MPI issues. Won't rev under load.

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454 MAG MPI issues. Won't rev under load.

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Old 08-16-2012 | 06:14 PM
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Yes, Redhook 98...Half way job gets half the results!

I broke a distributor cap bolt in my rush in the dark, so I was just happy with drilling, tapping, and getting it back together.

The cap was completly corroded, each blade, I wish I could find an easy way to post a pic., I would expect that amount of corrosion would put a hefty amount of resistance on the coil, so that's next. It ran a little better until Io went back to idle, then issues with stalling and wouldn't get up on plane.

I will next do the cap and coil and advise on any progress....
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Old 08-16-2012 | 06:15 PM
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Sorry, rotor and coil!
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Old 08-20-2012 | 09:16 AM
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Anybody ever had something like this simply because of bad gas? The boat ran perfect before that fill up. No misses at idle and she will rev all the way up and down smooth in neutral. runs fine in the water at slow speed but the engine just stops right at 2500 on the mark every time.
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Old 08-20-2012 | 09:24 AM
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Originally Posted by seansmp8
Anybody ever had something like this simply because of bad gas? The boat ran perfect before that fill up. No misses at idle and she will rev all the way up and down smooth in neutral. runs fine in the water at slow speed but the engine just stops right at 2500 on the mark every time.
My brother n law was having problems like this.. Slight miss at idle but you could barely tell and it wouldn't rev past 3800 or so.

ended up being bad injectors and the had 3 on one motor!!
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Old 09-06-2012 | 09:52 AM
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Default Still no power

OK, Now have replaced coil, distributor cap & rotor, plugs, & wires. I am now looking more at fuel issues. Local marina has a complete VST with new high pressure fuel pump, I am going to pop that in, if that's not the problem, I will pull the injectors - any other ideas?
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Old 09-20-2012 | 09:11 PM
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Default Fixed!

PROBLEM FOUND!

I bought a used VST with a new high pressure fuel pump installed, it solved the problem. I expect the issue was the fuel pump, it is possible that it was the O-rings in the VST.

The issue was a gas issue!

Thanks to all who posted and replied!
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Old 04-15-2014 | 01:54 PM
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Hey guys, bringing up my old thread, still having this issue. The boat sat all last year so I wasn't ablt to keep up on here. Any advice would help. I checked the cap and it looks fine, plugs are new. Hooked up a scan tool and didn't recieve any codes. I'm lost.
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Old 04-15-2014 | 02:29 PM
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VST pump or the VST screen is plugged.
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Old 04-15-2014 | 09:00 PM
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Coul be that the low pressure pump cant supply high pressure pump as well
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Old 04-16-2014 | 06:40 AM
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I pulled the hose off the low pump and put it in an empty 2ltr bottle, pulled the coil wire, and cranked it. It had a good flow and filled half the bottle up after a few. Seems to be fine there. I plan on checking the VST screen, is it just in the housing?
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