[Tinker51]

I have seen something similar with a friends jet boat once. Same symptom. No power above about 2800 RPM if you tried to get there quickly. If you eased into it the motor ran ok, not great but ok. After a TON of ignition diagnostics we found that there were no jets installed in the secondaries so when they opened up it was dumping way too much fuel. This was an old carb he had around so we never really looked that hard at it before installing it. We laughed like hell because we had exhausted all ignition possibilities (two days work) and out of sheer desparation we cracked the bowl on the carb and found the jets missing. If you have gone clear through the spark then you might have a fuel problem.