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I bought an older 750SS with KehninII carb. Compression was good and it runs well on low end to half throttle. Above half throttle the ski dies out as if it is either running out of fuel or losing spark on one cylinder. ( I suspect the first). When it does this If you back out of the throttle it "settles" out again and runs smooth. Here's what I have done. Compression test: 150 and 145. Disassembled and rebuilt carb/fuelpump with a new SBT kit, nothing "noticibly wrong" or clogged passages other than a small bit of debris/sand in the pump diaph., cleaned thoroughly and and blew out carb before reassembly. I set the screws where they originally were, ( High was 1.25 turns from seated, and low was 1.0 turn) Checked fuel lines, and valves, all seem ok. Water tested and have same results. I'm wondering if there is a screen in the tank that could be clogged, or am I going totally up the wrong tree here?? I work on inboards of the classic variety but these toys are new to me, so any help or suggestions would be appreciated. Any ideas??? Thanks in advance, Lee