2003 Mercury Bigfoot Fuel Issues! Please Help!

Joined
Jul 24, 2011
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19
I have a 21 foot pontoon with a 03 mercury 4 stroke EFI bigfoot. I have had the motor for the last two summers with no issues. All of a sudden today we were cruising about 5000 rpms and the boat just dropped to 1000. I went back and squeezed the primer bulb 4-5 times and off we went again for 4-5 minutes at 5000 then it dropped to 1000. Squeezed bulb again and made it back to the trailer. I ran home and grabbed my fuel pressure guage. Ran boat on gauge. 42psi at idle all the way up to 50 at WOT. After 4-5 minutes bam it dropped to 12psi and went right back to 1000rpm. I took it out of the water, changed the fuel bowl filter, opened up and cleaned the VST which was clean as a whistle, knocked out the anti bilge ball bearing at the tank and took her back to the lake. Same exact thing. 5000rpm for 4-5 minutes and back down to 1000 and it never stalls. What next?
 
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