Everything runs great at idle and in neutral the 502 revs rite up like it should but under load it is just not all there no backfires or anything just lacks power when planing off or at wide open. But here is the catch it only happens sometimes its intermittent and after about 45 min it becomes less frequent. So when the issue is not there the boat comes on plane like a jet ski and runs 60+mph but when its messing up its slow to plane and only hits 45 -50mph.Im thinking the knock sensor is getting a false signal ....sometimes can anyone give me some input