mercury outboard problem

by countryboy

02 mercury 40 hp four stroke efi motor boggs and losses power at WOT. Will idle fine but when i go to throttle it down it spits and sputters like a backfire. Took to mechanic and he said was locking in gaurdian mode and shuting motor down because of a faulty water pump,impeller ,etc. Got boat back from him $200 later and still doing same thing.I changed fuel filters one inline filter and the other the fuel/water filter.the mechanic also put fresh no e10 gas in boat with fuel treatment.Talk to another mechanic said sounded to him like a fuel delivier problem.and when it bogs and misses is what they call a cough/wheeze. and injectors needed cleaning. the thing that puzzles me though is i can take plugs out clean them with a little sandpaper make sure they are gapped good put them back in and it run like a champ for a little while till it does it again.Any help would be appreciated. i just cant afford to keep putting money in the motor and it not fix the problem.

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